452 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



In a recent number of these Proceedings Gerrit S. Miller, jr., has 

 described examples of divergent evolution under uniform environ- 

 ments in the color characters of the Malayan species of mouse-deer. 

 These are small, nocturnal, forest creatures whose inconspicuous habits 

 might be compared with those of the millipeds. 1 



It is the regular rule for related species of millipeds to show such 

 differences of color, not only in neighboring regions, but often in the 

 same localities. With the millipeds the general uniformity of habits 

 makes it also apparent that such nonadaptive differences are not 

 limited to small details of color or proportion, but include elaborate 

 structural specializations, characters of families and orders, as well as 

 of species and genera. 



While there can be no absolute certainty that any particular 

 specialization of a milliped or of any other creature is entirely useless, 

 and always has been, the range of speculation regarding the adaptive 

 value of characters is greatly narrowed because of the general uniform- 

 ity in the habits of the group, a uniformity that must be supposed to 

 have existed in the past as well as in the present. The general rela- 

 tion of natural selection to the evolution of the millipeds is not deter- 

 mined by the usefulness or uselessness of some particular character, 

 but is to be judged from the larger and more general fact that the 

 structural differentiation of the members of the group is out of all pro- 

 portion to their environmental differences. 



Even if it were to be admitted that natural selection had accom- 

 plished all that has been claimed for it in the evolution of special 

 characters in specialized environments, as in some of the higher groups, 

 such theories would still be inadequate to account for elaborate 

 diversification among the members of lower groups that have con- 

 tinued in essentially the same environments. General facts of the 

 ecology of whole orders or classes of animals and plants can be 

 appreciated, of course, only by those who have detailed familiarity 

 with such groups. The public can consider only the special cases that 

 may be adduced as illustrations. The example of kinetic evolution 

 afforded by the new Porto Rican milliped does not differ essentially 

 from many other examples of useless structural differences already 

 specified, but this case affords an unusually definite evidence of the 

 uselessness of a very elaborate structural specialization. 2 



The animal described below belongs to a cosmopolitan tropical 

 group (Stylodesmoidse) characterized by a peculiar roughening of 

 the dorsal surfaces of the segments by a dense felt of short hairs. 

 Small particles of earth are caught and matted into the hairs, so that 



1 G.S.Miller, jr., The Mouse-Deer of the Rhio-Linga Archipelago: A Study of Specific Differentiation 

 under Uniform Environment, Proceedings of the U. S. National Museum, vol. 37, 1910, pp. 1-9. 



>0. F. Cook, Evolutionary Inferences from the Diplopoda, Proc. Ent. Soc. Washington, vol. 5, No. 1, 

 1901, p. 14. 



