December 9, 1892.] 



SCIENCli 



325 



several improTements 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 move- 

 ment of the arm under the conditions present while writing, 

 another on the reaction-time to tones as dependent on pitch, in- 

 tensity, duration, etc. 



The ample accommodations furnished by the fifteen rooms, the 

 three months of energeiic preparation duiing the summer, the 

 high scientific stand taken in regard to research, the wise pat- 

 ronage of Professor Ladd and the enthusiasm of the young inves- 

 tigators lead us to hope that the first year will see us with a recog- 

 nized 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 phy- 

 sical 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 cross- 

 stitched rubber belting; E. B. Meyrowitz has sent a set of test- 

 cards, etc. More of such help woald be thankfully received ; at 

 present we need a * horse-power motor, a spark coil, etc. Pos- 

 sibly 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 COLA.PTES. 



BY SAMUEL N. RHOADS, ACADEMY OF NATURAL SCIENCES, PHILA- 

 DELPHIA. 



Perhaps the most widespread and persistent tendency to 

 hybridism that exists among the higher vAtebrates to-day is to 

 be found in this American genus of woodpeckers. The birds re- 

 sponsible for such a slate of affairs are well known in their re- 

 spective habitats as flickers, the eastern species being named the 

 yellow-shafted flicker (Colaptes auratus), and its western con- 

 gener, the red- shafted flicker (CoZapfesco/er) 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 cofer, as a distinct 

 species, naming it Picus ayresii ; but as more specimens were se- 

 cured it became evident that these intermediate birds were not 

 constant in character and their numbers were too great to be ex- 

 plained by any other theory than that they were the off.^pring 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 v\-ith 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 Cata- 

 logue, 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 pos- 

 sibly a "sign of reversion to remote ancestral plumage." 



East 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 N.itiiral Historv and being inaccessible 

 to the general reader may be brieflv summed as follows: — 



1. Mixed birds show no stages of g^og^aphic variation com- 

 parable with those connecting specie.^ and sub- species In the 

 latter the transition is gradual, symmetrical, and correlated with 

 change of environment, hut in ColapUs the intergradation is ir- 

 regular, often asymmetrical and without such correlation. 



2 Very unlike birds have been found to breed together; di- 

 verse offspring being reared in the same nest by parents indif- 

 ferently 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 upm the 

 other fades imperceptibly eastward and westward till it disap- 

 pears. 



4. The main area of hybrid distribution covers a belt of country 

 two hundred miles wide and reaching north-weslwardly fiom the 

 Gulf-coast of Texas through Colorado, Wyoming, Montana, 

 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 habi- 

 tat of true ciifer reaches from the Columbia to Tehuantepee, 

 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 thor- 

 oughbred birds are the exception. This favors the assumption 

 that auratus is extending its range iuto 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 evi- 

 dence which has induced Mr. Allen and the majority of orni- 

 thologists 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 re- 

 lieved 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, north- 

 western form of cafer found here has so thoroughly assimilated 

 the characters of auratus that cafer is the exception and cafer- 

 auratus the rule. Nevertheless, pure auratus is very rare on the 

 island. I have no specimens of it, but Mr. Fannin of the Vic- 

 toria 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 wiih 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, con- 

 tained in the collections of the Academy of Natural Sciences of 

 Philadelphia from debatable territory m the west and north- 

 west, 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 di- 

 rection 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 th s 

 case results in an overproduction of males or a disparity in tie 



