Abbildungen der Seite
PDF
EPUB
[graphic]

New Method of Protecting Property from Lightning.

The Lightning Dispeller.

Price, $20 to $30.-According to size.

The Patent Lightning Dispeller is a conductor specially designed to dissipate the energy of a lightning discharge,-to prevent its doing harm,-placing something in its path upon which its capacity for causing damage may be expended.

No recorded case of lightning stroke has yet been cited against the principle of the Dispeller. So far as known, the dissipation of a conductor has invariably protected under the conditions employed.

Correspondence solicited.

AGENTS WANTED.

Kohl of Chemnitz, Germany, we are enabled to
By the kindness of our correspondent, Mr. Max
present to our readers an illustration of a miniature
steam-engine, recently constructed in his establish-
ment. Although so small as to fit easily within its
little machine is a practical working model, correct-
case, composed of an ordinary walnut shell, the
ly and completely finished in all its parts. The
cylinder, which is supplied with a complete sliding
valve, is 5.5 mme. in length and has a bore of 2 mme.
The boiler is 20 mme. in length and 8.5 mme in
diameter. The diameter of the fly-wheel is 10 mme.
and that of the steam channels 0.2 mme The slide
is 1.8 mme. in length and 1.7 mme. in breadth. The
machine is furnished with safety valve, waste-cock
and funnel. The model is to be driven with a spirit

The American Lightning Protection Company, lamp, but it can also be put in motion by means of

United Bank Building, Sioux City, Iowa.

a thin rubber tube, the one end of which is to be
screwed in the funnel on the kettle, while the other
end is supplied with a mouth fr blowing air into
the kettle. The model only serves to show in what
made.

[blocks in formation]

small dimensions working steam-engines can be The

THE LABRADOR COAST. THE WINNIPEG COUNTRY;

A JOURNAL OF TWO SUMMER CRUISES
TO THAT REGION.

WITH NOTES ON ITS EARLY DISCOV-
ERY, ON THE ESKIMO, ON ITS PHY-
SICAL GEOGRAPHY, GEOLOGY AND
NATURAL HISTORY, TOGETHER WITH
A BIBLIOGRAPHY OF WORKS, ARTI-
CLES, AND CHARTS RELATING TO
THE CIVIL AND NATURAL HISTORY
OF THE LABRADOR PENINSULA.

OR,

ROUGHING IT WITH AN ECLIPSE PARTY.

With

BY

A. ROCHESTER FELLOW.
(S. H. SCUDDER.)

thirty-two Illustrations and a Map.
12°. $1.50.

"This is a sprightly narrative of personal inci-
dent. The book will be a pleasant reminder to
many of rough experiences on a frontier which is

rapidly receding."-Boston Transcript.

"The picture of our desolate North-western territory twenty-five years ago, in contrast with its the writer's style, constitute the claims of his little book to present attention."-The Dial.

By ALPHEUS SPRING PACKARD, M.D., Ph.D. civilized aspect to-day, and the pleasant features of

Sportsmen and ornithologists wil 10e interested in the list of Labrador birds by Mr. L. W. Turner, which has been kindly revised and brought down to date by Dr. J. A. Allen. Dr. S. H. Scudder has contributed the list of butterflies, and Prof. John Macoun, of Ottawa, Canada, has prepared the list of Labrador plants.

Much pains has been taken to render the bibliog

N. D. C. HODGES,
874 Broadway, New York, N. Y.

A TEMPORARY BINDER

Simplex Printer

A new invention for duplicating copies of writings or drawings.

[blocks in formation]

20 Vesey St., New York.

STERBROOK'S
STEEL PENS.

OF SUPERIOR AND STANDARD QUALITY.

raphy complete, and the author is indebted to Dr. for Science is now ready, and will be mailed Leading Nos.: 048, 14, 130, 135, 239, 333

Franz Boas and others for several titles and impor- postpaid on receipt of 75 cents.

tant suggestions; and it is hoped that this feature of the book will recommend it to collectors of Ameri

cana.

It is hoped that the volume will serve as a guide to the Labrador coast for the use of travellers, yachtsmen, sportsmen, artists, and naturalists, as well as those interested in geographical and historical studies.

513 pp., 8°, $3.50.

[blocks in formation]

N. D. C. HODGES, 874 Broadway, New York. N D. C. HODGES, 874 Broadway, New York.

Minerals,

Rocks,

Fossils,

Casts of Fossils,
Geological

Relief Maps.

For Sale by all Stationers.
THE ESTERBROOK STEEL PEN CO.
Works: Camden, N. J. 26 John St., New York.

WOODCOCK AND QUAIL -Gameland, the ilustrated magazine of shooting and fishing, tells you where to find these grand sporting bi ds in near-by and faraway localities. It is full of camp life, woodcraft, landscape and natural history. By the year, One Dollar. Three months' trial subscription, 25 cents. Address GAMELAND, 1,267 Broadway, New York, N. Y.

[blocks in formation]

SCIENCE

8637.

[blocks in formation]

portrays them as seen from the flat roof of the Warner Observatory with an unobstructed horizon. Two of these exhibitions I consider unique if not unexampled.

On the evening of June 16, just before midnight, turning my eye from the telescope, a bright narrow beam of light was seen extending from the western horizon to an elevation of some 50°, at right angles to the magnetic meridian, and, of course, parallel with its equator. Here it divided into six parallel bands or branches, like six gigantic fingers of an outstretched hand, which continued to 5° beyond Alpha Cygni, or to a length of more than 60°, when they all sharply ended (Fig. 1). After a visibility of about twenty minutes it slowly disappeared, and was the only sign of aurora observed during that entire night.

Again, at early twilight on the evening of July 16, a portion of a faint auroral band some 15° in length was observed just south of Alpha Aquilla, having on the south side two, and on the north,

[blocks in formation]

one short, narrow band close to, though not touching, the principal one. This, being so far south, was of itself an uncommon occurrence, and, as twilight deepened into night, a slender stem not exceeding 15° in width issued from the western end and gradually lengthened, curving to the south-west and south until, like a mighty sickle, the band serving for a handle and the curved ray for its cutting blade, it reached nearly to the south-western horizon (Fig. 2). It lasted about a half-hour, growing brighter and longer as twilight increased, when it quite suddenly disappeared. Immediately after, a rosy cloud and tinted streamers

appeared in the north west, and the grandest auroral display of the century commenced.

During thirty five years of out-door night work I have never seen any auroral phenomena at all resembling these two instances, and would much like to know if these appearances were witnessed by other observers elsewhere

A perfect auroral exhibition consists of at least ten distinct phenomena. It is very seldom, however, that all or even a majority of the requisites are present at any one display. They are here named in the order of their most usual appearance: 1, evenly diffused light in the north; 2, a dark arch whose apex is in the magnetic meridian; 3, streamers; 4, luminous patches, especially in the north-west, sometimes of a red color, often for a long time stationary; 5, colored patches and streamers; 6, merry dancers; 7, corona in the magnetic meridian and equator, the point where the streamers seem by perspective to converge; 8, streamers issuing south from the corona, occasionally extending to near the southern horizon; 9, curtains, with frilled, wavy edges, apparently suspended from the sky; 10, narrow luminous bands, often reaching from the eastern to the western horizon, always at a right angle to the magnetic meridian, but seldom, if ever, coincident with its equator.

As seen from this station by myself, my assistant, and a friend, all of the above features, save the hanging curtains, were simultaneously visible.

That there is a connection between the aurora and sun-spots is quite generally conceded, though denied by some eminent authorities. We know that aurora frequently occur when no spots are visible on the sun, and that sun-spots are often seen when auroral exhibitions, either boreal or austral, are entirely absent, but to this the advocates of the theory make answer to the former that sun-spots may have been on the other side of the sun, and, to the latter objection, that there may have been auroræ visible only in the Arctic or the Antarctic regions, or in both, But there is need of further confirmatory evidence by the general co-operation of astronomers in the collection of enlarged data for the establishment, modification, or complete rejection of the prevailing theory that sun-spots, auroræ, and terrestrial magnetism are intimately connected.

Intelligence has just reached me that the famous display of July 16 was also witnessed from the southern hemisphere on a scale of grandeur comparable to our own. This simultaneity of the phenomena at both terrestrial poles suggests the question whether this is always the case.

When the writer was a lad, in perhaps the year 1834 or 5, the sky being densely cloudy and the ground covered with snow, he saw at eight o'clock one evening every visible object, especially the snow and sky, suddenly assume a bright crimson red. He wonders if any reader of Science recalls that memorable spectacle which appalled so many people. He does not remember to have ever seen an explanation of the ghastly phenomenon from any country where the sky was cloudless, but it was, doubtless, caused by an extraordinarily tinted aurora.

BIOLOGICAL NOTES FROM NEW ZEALAND.

BY GEO M. THOMSON, DUNEDIN, N.Z.

A VERY interesting feature in connection with the flora of New Zealand is the rarity of those plant structures which are correlated with the presence of mammalia. If we except the spiny Aciphyllas, there is not a single species of plant peculiar to these islands which shows any contrivance either for distribution by, or protection against, mammals, even where other species of the same genus are so modified in other parts of the world. Aciphylla is a

[ocr errors]

genus of tall, rigið, umbelliferous plants, peculiar to the islands, with the exception of a rare and feeble species which occurs on the mountains of eastern Australia. The leaves and bracts of two of the species, in all their subdivisions, end in long, rigid spines, rendering them most formidable plants. The only suggested explanation for the occurrence of such strongly-armed species is that they were thus protected against the moas. This may or may not be true. It may be said in favor of the hypothesis that the moas were extraordinarily abundant in former times and they were vegetable feeders, the contents of their crops, consisting of rounded pebbles and comminuted vegetable fibres, being commonly found. It is also the case that since the introduction of pigs into the colony, these plants have been immensely reduced in numbers. The pigs root up the ground at some little distance from the plant, and so get at it from below.

But, leaving this exceptional case, we find the general statement true with which this note is prefaced. A few examples may be given. The genus Acana consists of small rosaceous herbs which have undergone considerable retrogressive development. The name refers to the spines, formed of the four produced and hardened persistent calyx-lobes which project above the fruit. Of the five species found in New Zealand, two have a wide distribution outside the islands; A. sanguisorbæ ranging westwards across Tasmania and Australia, and reappearing in Tristan d'Acunha; while A. adscendens is a more Antarctic type, occurring in the Macquarrie Islands, Tierra del Fuego, and the Falkland Islands. In both these species the calyx spines are tipped with small barbed hairs, by means of which the fruit adheres to any passing animal with great persistence. In the other species of the genus which are peculiar to New Zealand, the spines have almost or altogether lost the barbs and the fruit is not distributed widely. The change is not, however, complete in all; thus in A. microphylla the spines are strongly developed and occasionally have reversed hairs on their summit. In A. Buchanani the spines are feeble and rarely have a few apical hairs, but sometimes they are not developed. Lastly, in A. inermis the calyx merely has its angles thickened in fruit, and there are no spines.

The only other New Zealand plants in which the fruit is carried by means of barbs which could catch on to passing animals belong to the genus Uncinia a group of sedges which have the utricle furnished with a long barbed bristle or seta. This forms a most efficient organ for hooking hairs, etc., and it renders the fruit a great pest to dogs. The New Zealand species are, as Hooker says, "difficult of discrimination," and some are so closely allied to Tasmanian or to South American forms as to be almost indistinguishable The genus is widely spread in the Southern Hemisphere, and also occurs as far north as the mountains of Abyssinia. It is clear that the barbed bristle is a character developed outside of these islands and is evidently of great antiquity. In some of the more slender endemic forms it is not very strongly developed, but I know of no species which has lost it.

Spiny and prickly plants are very rare, and, with the exception of the Aciphyllas already mentioned. are all Australian. Discaria toumatou is probably the same as the Australian D. australis; in this plant the leaves are small, and the branches are developed into strong spines which protect it against grazing animals. Eryngium vesiculosum is a low-growing umbelliferous plant with very prickly leaves and bracts, but it is a common Australian and Tasmanian species. The same remark applies to Rubus australis, but in this case the formidable, recurved prickles, which have earned the plant the name of "bush lawyer," are chiefly of service as climbing organs. There is, indeed, no endemic spiny plant in New Zealand (except Aciphylla).

The tendency to lose the protective character is shown in a most instructive manner in a few instances. Thus there are in these islands two species of the myitaceous genus Leptospermum. L. scoparium, which is also common in Tasmania, has rigid, pungent leaves, which only an animal with a hard palate could attack with impunity. On the other hand, L. ericoides, which is confined to the islands, has quite lost the pungent tip to its leaves, and the foliage and branches are much softer and less rigid.

An exception to the rule here exemplified is afforded by the tles, of which one endemic species, Urtica ferox, is about as

diabolical a species as can be met with. Its long, stinging hairs inflict a painful wound. It is difficult to say what they serve to protect the plant from. As if to show that perfection of protective development in one direction does not always serve in another, it is a fact worth noting that this species is so very much attacked by leaf-eating insects that it is often a matter of difficulty to get herbarium specimens quite perfect.

THE PSYCHOLOGICAL LABORATORY AT YALE.

FOR several years Professor Ladd has been lecturing on physiological psychology, using charts, models, microscope slides, etc., for illustration. His earnest desire to have a laboratory for this science finally met its fulfilment last spring. The second, third, and attic floors of a building were given for that purpose, and $1,500 were appropriated for equipping the apartments and for apparatus. Dr. E. W. Scripture, a pupil of Wundt in Leipzig, was called from Clark University to take charge. Orders for apparatus were sent off at once, and the preparation of the rooms went on all summer, so that the work of instruction and research began without a hitch on the first day of the term.

The laboratory consists of fifteen rooms, among which are the lecture room, seminary room, library, chemical, and battery rooms, apparatus room, isolated room, time room, generalresearch room, and workshop. The workshop contains a screwcutting lathe and all tools that can be desired for the repair and manufacture of apparatus. A regular mechanic is at work here part of the time. This workshop, which is the most complete one ever put into a psychological laboratory, is regarded as the foundation of research and demonstration work. The plan followed in investing the funds has been to spend as little as possible for mere demonstration apparatus and to reserve nearly all for research work; nevertheless it is of supreme importance to have the lectures on psychology consist almost entirely of demonstrations. This difficulty has been completely solved by the workshop where the apparatus for demonstration is put together or manufactured with sufficient care for the purpose.

Three rooms, including the isolated room, are given over entirely to research. This isolated room is a small room built inside of another room; four springs of rubber and felt are the only points in which it comes in contact with the outer walls. The space between the walls is filled with sawdust as in an ice-box. The room is thus proof against sound and light, and affords an opportunity of making more accurate experiments on the mental condition than yet attempted.

A particularly new feature is the electrical communication between the rooms. It is nearly always necessary to separate the experimenter from the one experimented on; in order to avoid the large number of electrical wires necessary to connect the rooms separately a switchboard has been arranged similar to a telephone switchboard, to which sets of wires run from each room. But this one with fifty-six wires has been put in with the aid of a carpenter at about one-tenth the cost of a telephone-board.

The following courses are given in the laboratory by Dr. Scripture: 1. A regular lecture course in experimental and physiological psychology of one hour per week, for seniors and graduates; the seniors alone recite on another day. 2. A laboratory course in experimental psychology for graduates, conducted on the seminary method by the men themselves. The object is not only to give a thorough knowledge of the psychological work in the laboratory, but to train the men in handling apparatus and in conducting lectures, thus providing a supply of instructors ready to take positions. This course has seventeen members, being exceeded in the graduate department only by Professor Ladd's philosophical courses. 3. Research work. It is the constant en deavor to awaken in the students the spirit of original investigation, this being what America most lacks in its educational life. Men are also encouraged on the principle that one learns most by doing. Last, not least, the fact is recognized that the amount of research done determines the standing of the laboratory in the scientific world. Already six original investigations of the highest class are under way; they include one on attention, in which

several improvements in apparatus and methods of experiment have already been made, one on the time of action and the fatigue of monocular accommodation, another on the rapidity of movement of the arm under the conditions present while writing, another on the reaction-time to tones as dependent on pitch, intensity, duration, etc.

The ample accommodations furnished by the fifteen rooms, the three months of energetic preparation during the summer, the high scientific stand taken in regard to research, the wise patronage of Professor Ladd and the enthusiasm of the young investigators lead us to hope that the first year will see us with a recognized standing, second only to Wundt's laboratory at Leipzig. Nevertheless, there are many difficulties to be overcome; the work of instruction really requires as full an equipment as a physical laboratory; moreover, research is the most expensive kind of work, thus putting a great strain on the appropriation. It would be a very great help if some one or more friends would undertake to support or aid some one of the researches, setting any desired amount as the limit beyond which the expenses are to be paid by the laboratory. We have already received considerable aid in our work: Professor Ladd has given the laboratory his valuable collection of charts and models and a microscope; a friend has donated $75 for electric forks required in one of the researches; the B. F. Sturtevant Co. has sent a rotary blower; the Electric Gas Lighting Co. of Boston has sent a dozen Samson batteries; the Aluminium Brass and Bronze Co. of Bridgeport has made us a dozen discs twelve inches in diameter; the Boston Woven Hose and Rubber Co. has furnished some of their crossstitched rubber belting; E. B. Meyrowitz has sent a set of testcards, etc. More of such help would be thankfully received; at present we need a horse-power motor, a spark coil, etc. Possibly the day is not far distant when an endowment will be made for a separate building and a full equipment of apparatus.

HYBRIDISM EXEMPLIFIED IN THE GENUS COLAPTES. BY SAMUEL N. RHOADS, ACADEMY OF NATURAL SCIENCES, PHILA

DELPHIA.

PERHAPS the most widespread and persistent tendency to hybridism that exists among the higher vertebrates to-day is to be found in this American genus of woodpeckers. The birds responsible for such a state of affairs are well known in their respective habitats as flickers, the eastern species being named the yellow-shafted flicker (Colaptes auratus), and its western congener, the red-shafted flicker (Colaptes cafer) by naturalists.

It early became known to explorers in the upper Missouri and Yellowstone regions of this country that where the habitats of these red- and yellow-shafted birds adjoin there often occurred individuals partaking the characters of both species. Audubon described in the appendix to his "North American Birds," a flicker from this region, with the yellow shafts and red nape of auratus combined with the red mustaches of cafer, as a distinct species, naming it Picus ayresii; but as more specimens were secured it became evident that these intermediate birds were not constant in character and their numbers were too great to be explained by any other theory than that they were the offspring of distinct species and were hybrids. Professor Baird enunciated this idea in 1858, classing for convenience all these nondescripts under the distinctive name of Co'aptes hybridus, and asserting that their existence could be satisfactorily accounted for in no other way. The amount of material on which he based his theory, however, was small enough to warrant other theories, Mr. J. A. Allen attributing the existence of so-called hybridus" to the "action of environment in accordance with certain laws of geographic variation," and later Mr. Ridgway suggested they were remnants of a generalized form from which two incipient species have been differentiated." Dr. Coues, in 1884, thought the mixed birds might constitute "perhaps a hybrid and perhaps a transitional form," while Hargitt, in the British Museum Catalogue, makes the intermediates a race with the nominal status of a species under the Audubonian name of ayresii, admitting them to have been originally the result of a mixed union, showing possibly a "sign of reversion to remote ancestral plumage."

Last year (1891) Mr. J. A. Allen made the relationships of the whole genus the subject of an exhaustive study. The results of his examination are given in full in Vol. IV. of the Bulletin of the New York Museum of Natural History and being inaccessible to the general reader may be briefly summed as follows:

1. Mixed birds show no stages of geographic variation comparable with those connecting species and sub-species. In the latter the transition is gradual, symmetrical, and correlated with change of environment, but in Colaptes the intergradation is irregular, often asymmetrical and without such correlation.

2. Very unlike birds have been found to breed together; diverse offspring being reared in the same nest by parents indifferently exhibiting normal or abnormal characters irrespective of sex. But so far typical cafer and auratus have not been found paired together.

3. On either side of the boundary of one thousand miles, along which their habitats adjoin, the influence of one species upon the other fades imperceptibly eastward and westward till it disappears.

4. The main area of hybrid distribution covers a belt of country two hundred miles wide and reaching north-westwardly from the Gulf-coast of Texas through Colorado, Wyoming, Montara, northern Idaho and Washington and the southern half of British Columbia to the Pacific, extending from southern Alaska to the mouth of the Columbia River. South and west of this the babitat of true cafer reaches from the Columbia to Tehuantepec, while north and east of it pure auratus ranges, over an area four times as great, from Florida to Hudson's Bay and from Labrador to Behring Sea.

5. Formerly, collections from certain parts of the far West, notably California and Nevada, were wanting in hybrids, but now they have become so common in some localities that thoroughbred birds are the exception. This favors the assumption that auratus is extending its range into the cafer region, and the absence of such an invasion of mixed individuals northward indicates that the transmigration is in the historic direction, from north to south.

This, with a few interpolations of my own sums up the evidence which has induced Mr. Allen and the majority of ornithologists to adopt Baird's theory to its fullest extent.

To this I wish to add a few supplementary remarks based on a collection of flickers made this year in British Columbia. As this series was chiefly collected in the breeding period we are relieved of the complications caused by the winter migration of Alaskan auratus into the region and can rely on the specimens as representing the domestic relations of the group.

Perhaps nowhere is the proportion of hybrids to pure-bred birds greater than on the Island of Vancouver. The dark, northwestern form of cafer found here has so thoroughly assimilated the characters of auratus that cafer is the exception and caferauratus the rule. Nevertheless, pure auratus is very rare on the island. I have no specimens of it, but Mr. Fannin of the Victoria Museum has one, and Mr. Maynard of the same city states they are sometimes numerous in the fall. I am, however, from the absence of such specimens in collections, inclined to discount this statement, in the belief that they will prove to be of impure origin also. Indeed it is doubtful if there is much association, much less admixture, of thoroughbred individuals of the two species either with each other or with hybrids at the present day, many which appear pure, especially among the females, being of impure extraction.

Comparing the results of an examination of seventy skins, contained in the collections of the Academy of Natural Sciences of Philadelphia from debatable territory in the west and northwest, with the deductions given in Mr. Allen's admirable paper, the following general remarks seem in order:

1. The prevailing tendency among hybrid flickers is in the direction of a symmetrical assumption of the characters of both species, examples of asymmetric coloration being rarely present and chiefly confined to the females.

2. A much larger percentage of male than female birds show mixed parentage. This indicates either that hybridism in this case results in an overproduction of males or a disparity in the

relative numbers of the sexes among these hybrids, or it is due to the fact that females assume abnormal secondary sexual characters less readily than males. Until it be proven that hybridism does cause a disparity in the numbers of the sexes we may safely accept the latter explanation.

3. The preponderance of hybrids showing typical coloration of cafer combined with the red nuchal crescent of auratus contrasted with the scarcity of those showing the yellow and black characters of auratus shows a predisposition to acquire red in that part quite in accordance with the general law of coloration in the Picide, and may be considered a reversion to the characters of some common tropical ancestor from which the two species have originally been derived.

4. This tendency to assume red in preference to yellow or black colors fully accords with the southern dispersion of hybrids into cafer territory as contrasted with their non-dispersion into auratus territory.

5. The absence of records of pure auratus and cafer birds pairing together, and the abundance and evident fertility of the hybrids in some regions indicates the majority of hybrids are mongrels, i. e., the offspring of hybrid parent or parents as distinguished from those generated by distinct species.

6. It has been determined' that mongrels show a stronger tendency to revert to the characters of either parent than do hydrids. In cafer auratus this would result in the final elimination of the hydrid element among these species. But we have seen that the tendency is toward an increase of this element.

A probable explanation of this may be found in the non appearance of mixed characters in female hybrids by which pure bred males are readily induced to pair with them and renew the tendency to variability.

Among the most significant queries which spontaneously arise in the mind regarding the case in hand, we may consider the following with possible profit: first, how did it happen? second, when did it happen? third, what will be the result? and fourth, what part has hybridization in the evolution or extinction of species?

Bearing upon the first question the effect of migration is of special import. In general, flickers are very hardy birds, able to resist the severest weather in sheltered localities as far north as the forty-fifth parallel. Over the country south of this the migration is less a southerly movement than a descent from the mountains into the valleys and a retreat to the densely wooded regions of the sea-coast. That the same conditions prevail on the Pacific coast I am assured by Mr. Fannin.

In the vast central territories of the continent north of the Rocky Mountains the southerly migration is more decided and far-reaching. A look at the map will show that the Rockies, after extending nearly due north through the United States from the headwaters of the Rio Grande to the northern boundary, suddenly contract from their easterly amplification in Montana and incline far to the north west through British Columbia. South of the boundary along the eastern and western slopes of this vast land mark the migrating hosts of interior flickers of each species would respectively pass without much admixture. But in the headwaters of the Missouri region this movement becomes more complicated owing to the westerly configuration of the mountain system and the corresponding westward extension of the habitat of auratus north of it toward southern Alaska. Here the migratory movements of auratus first assume the character of an actual invasion of the habitat of cafer, and as we go further west the southerly migration of auratus from Alaska is directed by physiographic and climatic conditions to the shores of the Pacific, along which, from Sitka to California, resides the darker race of cafer known as Colaptes cafer saturatior.

It is here that conditions exist more favorable to hybridism between cafer and auratus than anywhere else along the frontier of their common distribution, and it appears extremely probable that the north-west coast of British Columbia was the first witness to their notorious alliance.

Viewed thus, the history of the distribution and evolution of these species over North America becomes of special interest. 1 Origin of Species, p. 261.

Starting with a common ancestry in the tropics and diverging northward over the great eastern and western mountain systems of the continent, they became differentiated in accord with the dissimilarity of their environments.

Readily adaptable to extremes of climate, both forms rapidly extended their northerly range into the border lands of the glacial epoch, auratus following its receding pathway along the Appalachian system into the Canadian lowlands and across British America in the westerly direction of the Boreal life zone, while cafer, spreading over the table lands of Mexico and across the Mexican boundary, reached the west base of the Rocky Mountains, between which and the Pacific it continued to extend until the changed climatic conditions of the North Pacific coast were encountered. From this point, having assumed the darker coloring of Cleoptes cafer saturatior it rapidly extended, under more favored circumstances, until it met the southward migration of Alaskan auratus with the result already described.

Bearing upon the second question, that of chronology, we have first pretty sure evidence of a recent extension of the habitat of auratus into more southern territory, where it had not formerly been recorded. Coupled with this is discovered a growing abundance of hybrids in the same region, indicating an aggressive movement of auratus into new territory.

From the rate of this movement and the breadth of common ground over which these hybrids breed it would appear to be of comparatively recent inception, possibly within the last few bundred years.

Owing to the scarcity of intermediate birds in what is considered the rightful habitat of auratus, the transmigration has apparently come from the north and east, over neutral territory, until the habitats of auratus and cafer adjoined along a line considerably east of the base of the Rocky Mountains, following their extension into British America and crossing them about latitude 33 to the Pacific coast. At this phase of their history the two species were probably unadulterated, the mountains continuing in a modified degree to act as a natural barrier to their further extension. These conditions having now made possible the acquaintance of the species, it is for us to examine whether there were any characters shared by them in common which would predispose the birds to more intimate relations and account for their apparently anomalous conduct. As a result we find that in habits, language, size, proportions, physique, and pattern of coloration the two species are indistinguishable, while in color alone they are different. If we take any animal (man included), and endeavor to bring about a union between different species of the same genus we find that in proportion as the parties to such union resemble each other in habits, language, etc., as above given, they will the more readily accept the situation, other considerations being of no great importance.

This much as regards not only the possibility but the probability of a voluntary union between species so circumstanced. I think we must consider the interbreeding of any two species subjected to similar conditions as not only possible but inevitable. It is not in this respect that the hybrid flickers of North America are unique, but in their persistent fertility and wholesale reproduction over a large area. While this instance has no parallel on so grand a scale in the present history of species, so far as known, it is likely that similar conditions have been and are exerting an important influence in the evolution of life as we now sec it.

If this be true, we cannot too curiously consider the relationships of our eastern and western flickers, as time goes on, to determine if possible the laws which govern the progress of interbreeding of species in their natural state and whether they show that hybridization has any part in the evolution of new forms or the extinction of the old.

As observed, the present tendency in Colaptes resolves itself into an invasion of the hardier northern race upon their counterparts of the south, with the ready absorption of the characters of the former by the latter. This cross-breeding, in accord with laws now recognized, should produce mixed birds superior in some respects to their parents, combining the hardihood of auratus with the handsomer coloration of cafer and aggressively extend

« ZurückWeiter »