563 



THE AMERICAN NATURALIST 



[VOL. LI 



season of the year seems not to influence the occurrence 

 of regenerating specimens. 



The criterion of regeneration in these cases consists in 

 the presence of an anterior or posterior terminal part of 

 the body characteristically different in appearance from 

 the normal buccal or cloacal end, the surface being clearly 

 marked off from that of the rest of the body. In typical 

 examples these regenerated ends of the animal are more 

 sharply pointed than is usual ; they bear feebly developed 

 tentacles (at the anterior end), tube feet, and dorsal 

 papillae, which are less reactive than those on animals 

 judged to be not regenerated ; and these appendages are 

 very lightly pigmented (Fig. 1). These characteristics 



a b 



FIG. 1. Regeneration found occurring naturally. Semidiagrammatic sketches, 

 showing differences in pigmentation of a, cloacal end, b, oral end. Natural size. 



undoubtedly become less prominent with time, the colora- 

 tion tending, however, to remain pale on the ventral sur- 

 face (trivium). The first pigment to appear is the green 

 fluorescent one (cf. Crozier, 1914, p. 9 and 19156) ; the 

 dark brown substance develops more slowly, just as in 

 the growth of the post larval holothurians of this and re- 

 lated species. The spicules of the podia and skin seem 

 fewer than in corresponding non-regenerating parts, but 

 are of the usual sizes and shapes. The tentacles on re- 

 generating buccal ends are always fewer (9-15) than on 

 the normal individual (20). 



