134 



SCIENCE. 



[N. S. Vol. XIX. No. 473. 



to have the large place and concern in the 

 literature of evolution which it at present 

 occupies, as expressive of which such well- 

 known phrases as 'protective coloration,' 

 'warning colors,' 'mimicry,' etc., have 

 come to be household commonplaces among 

 us. It is not surprising, therefore, that 

 in a book like Wallace's 'Darwinism' out 

 of a total of some 475 pages more than 150 

 should be devoted to this phase of the 

 problem alone, while it has frequent ref- 

 erence in other connections. 



And the same is largely true of miieh 

 of the literature dealing with the sub.ject 

 of organic colors. In other words, color 

 in these relations has been studied largely, 

 if not wholly, as a factor in adaptation — 

 fitting the animal better to meet the exi- 

 gencies of life in the struggle for exist- 

 ence, in certain cases serving as a disguise 

 or screen against detection, in others by 

 glaringly advertising some noxious qual- 

 ity, in still others by flying a signal of 

 alarm or warning, and in flight serving to 

 segregate the members of a herd in whose 

 collective aggregate a larger measure of 

 protection might be realized. 



Hence it naturally came to pass that 

 color was looked upon largely as a physical 

 factor in the sum total of the animal's 

 morphology which must have some funda- 

 mental relation to the adaptation or fitness 

 for survival of the species. It is not 

 strange, under prevailing conditions, that 

 small attention was directed to the more 

 fundamental problem of the physiological 

 significance of color, or the part it has to 

 do in the processes of metabolism of the 

 individual organism. Recent work in ex- 

 perimental morphology has directed atten- 

 tion to this phase of the problem, and one 

 of the objects of the present discussion will 

 be to make somewhat more evident a too 

 long neglected aspect of animal biology. 



It ought not to be overlooked in this con- 

 nection that along with the development in 



experimental morphology to which refer- 

 ence has been made, those of organic chem- 

 istry, and particularly chemical physiol- 

 ogy, have been perhaps equally important 

 in directing attention to certain phases of 

 our problem. Nor ought we to forget that 

 the spectroscope has thrown its light upon 

 the same general problem, though with 

 perhaps less of conclusiveness than could 

 have been desired. As a result of this 

 growing activity there has been accumu- 

 lated a body of information, a part of 

 which stands directly related to the sub- 

 ject under consideration, and a part indi- 

 rectly concerned with the same essential 

 principles, and from it we may safely pre- 

 dict the solution of problems hitherto only 

 predicated hypothetically, and such side- 

 lights upon others equally important that 

 it is not too much confidently to forecast 

 substantial progress all along the line. 



It may be well in this connection to 

 glance briefly at some of the results at 

 IDresent known as in some measure justify- 

 ing these somewhat optimistic assumptions, 

 as well as pointing the line along which im- 

 portant and promising researches may be 

 prosecuted. 



The work of Krukenburg, MacMun, Ma- 

 callum, M'Kendrie, Hopkins, Urech, Eisig, 

 Cunningham and a host of others, com- 

 prising a mass of literature of enormous 

 proportions, will be available to those in- 

 terested and may afford some faint con- 

 ception of the magnitude and importance 

 of the field to be explored, as well as an 

 introduction to that already made avail- 

 able. And while as a result of this activity 

 many and various organic pigments have 

 been isolated and their composition in part 

 or entirely made known, it must be recog- 

 nized that the task of the chemical analy- 

 sis of any such highly complex compounds 

 as most of these are known to be is at- 

 tended with extreme difficulty and no 

 small measure of uncertainty. Still, it 



