THE HABITS OP FIDDLER-CRABS. 131 



the walrus's tusks. Among higher animals in which the males 

 possess such special aggressive organs, however, the females are 

 protected and cared for to some extent, but nothing of this sort 

 is known among decapod crustaceans with secondary sexual 

 adaptations (Uca, Alpheus, and others). Thus, although many 

 of the Crustacea have two adaptations which might fit them for 

 colonial life — through the mother carrying her eggs and young 

 for a time, thus having opportunity to start a colony with them ; 

 and through the aggressive adaptations of the males, which 

 might enable stronger individuals of that sex to gather a number 

 of females about them — their instincts have prevented them 

 from developing it. 



The writer can not believe with Alcock ('92) who thinks "no 

 one can doubt that the claw of a male has become conspicuous 

 and beautiful in order to attract the female" and that "it is used 

 as a signal to charm and allure the females." In support of 

 Alcock's views we have: (1) his ovvti opinion, which, though 

 apparently the result of more or less casual observations (p.l27) , 

 is not to be taken lightly; (2) the conclusion of the writer from 

 his observations at Manila that the colors of male fiddlers are 

 perhaps most uniform on the great chela and more variable on 

 other exposed parts of the body. Against Alcock's views may 

 be urged: (1) that during the most ardent courtships observed 

 by the writer (p. 127), the males kept their backs constantly 

 toward the females so that the great chela could not be seen; 

 (2) the chela is not always "bright" colored, at least as seen by 

 the human eye, and the males that danced were not always 

 bright; (3) other Crustacea depend little if at all upon the sense 

 of sight in choosing mates (Bethe, '97; Holmes '03; Pearse, '09; 

 Chidester, '11), and there is some doubt as to the ability of 

 crustaceans to discriminate colors (Pearse, '11) ; (4) at Manila 

 the female fiddlers often were, to the human eye, more brightly 

 colored than males of their ovrai species, and the female's bright 

 colors were on her back and legs so that they could readily be 

 seen by a male dancing behind her but she did no dancing. The 

 writer is convinced that the male dances about the female in 

 order to induce her to mate with him, but, from his own obser- 

 vations, doubts whether the male's coloration is effective in 

 influencing her to do so. The matter ought to be reexamined 

 during the active mating season with special reference to color. 

 By observing the coloration of the males actually chosen, by 

 painting the chelae of rejected suitors, or by other tests, a 



