January 22, 1904.] 



SCIENCE. 



143 



come 40 play a secondary function as a 

 sex character. 



What shall be said of such forms as 

 Bipalium and Geoplana among land plan- 

 arians, which exhibit in many cases bril- 

 liant coloration, but since they are chiefly 

 nocturnal in their habit and conceal them- 

 selves during the day under logs or other 

 cover, the color could hardly serve any 

 selective or adaptive function? 



The same is equally true of such forms 

 as nemerteans whose habitat is beneath 

 the sand along the tide line or below, and 

 also of many annelids having a similar 

 habitat. Some of these, particularly 

 among the latter, have types of coloration 

 which are often of brilliant character and 

 splendid patterns, vying, as one writer has 

 expressed it, 'with the very butterflies.' 



It can not be questioned that in some 

 cases we flnd among these forms what 

 would seem at first sight to be splendid 

 illustrations of protective coloration. If, 

 however, we trace in detail their distribu- 

 tion and variable habitat we shall often 

 find, as did Semper in the case of Myxicola, 

 that the supposed case of marvelous mim- 

 icry resolves itself into merest coincidence. 

 This case cited by Semper is described in 

 detail in 'Animal Life,' and its careful 

 study by some of our over-optimistic selec- 

 tionists would prove a healthy exercise, 

 conducing to a more critical scientific 

 spirit and, as a consequence, to saner inter- 

 pretations of appearances in the light of 

 all the facts. 



The mimicry in the case was of coral 

 polyps among which the annelid was 

 fo\md growing and which, in the form of 

 its branches, their size and coloration, 

 seemed so perfect that it had long escaped 

 notice and was described by Semper as a 

 new species. 



It was found in various localities among 

 the corals, but invariably having precisely 

 the same simulation of the polyps, so that 



Semper noted it as among the finest cases 

 of mimicry which had come to his atten- 

 tion. It so happened, however, that soon 

 after he happened to discover his mimetic 

 Myxicola growing upon a sponge whose 

 color and form were so dift'erent as to ren- 

 der it very conspicuous. A systematic 

 search for it in other situations soon re- 

 vealed it among the rocks, and in his own 

 language, 'Almost everywhere, and wher- 

 ever I examined it carefully, it was exactly 

 of the size and color of the polyps of Cla- 

 docora ccespitosa.' 



Attention has already been called to 

 Eisig's account of coloration among the 

 Capitellidffi, in which he discards the fac- 

 tor of natural selection as wholly inade- 

 quate in the case of the organisms under 

 consideration as well as in many others, 

 and refers to many investigators who have 

 likewise found it deficient. In his exhaus- 

 tive monograph the subject is discussed in 

 considerable detail and references given, 

 which it would be impracticable to cite in 

 such a review as the present. 



It will be possible to I'efer but briefly 

 to another group or two in the present dis- 

 cussion, the first of which is the echino- 

 derms, and chiefiy the starfishes. As is 

 Avell known, these organisms exhibit a con- 

 siderable range of variety and richness 

 of coloration, among which red, orange, 

 brown, yellow and black are more or less 

 common. In not a few cases of course the 

 colors comprise combinations of two or 

 more of those named. An examination has 

 been made of these pigments in a few cases 

 and has sufficed to show that for the most 

 part they are lipochromes and, therefore, 

 belong to either reserve or waste products. 

 Similar colors are also found among the 

 brittle-stars, with occasional admixtures of 

 blue or green, colors less common in the 

 former group. 



As is also well known similar colors are 

 found among the Crustacea, into a consid- 



