No. 646] SHORTER ARTICLES AND DISCUSSION 479 



somewhat misunderstood. In another connection I shall de- 

 scribe several aspects of the reproductive activities of these ani- 

 mals, the present remarks having to do merely with the act of 

 fecundation. 



Although it has commonly been held that the liberation of 

 eggs by a female chiton is due to the reception of spermatic 

 fluid diffusing into her respiratory water-currents from a near- 

 by male, the process of fertilization would appear in fact to be 

 initiated in a quite different manner. Stated briefly, the pres- 

 ence of one or more neighboring females serves in some way to 

 activate the discharge of sperm by the males, the spermatic 

 substances secondarily inducing the liberation of eggs. Nor- 

 mally this occurs only at those periods when the flow of the 

 tide begins just before sunrise, the shedding of the genital 

 products commencing as the chitons become covered by the sea. 

 The discharge of sperm can, however, be induced artificially at 

 certain times, in the laboratory, even a month or more before 

 the eggs are matured.^ A method which several times yielded 

 this result consisted in keeping some male chitons in a damp, 

 darkened vessel for about 14 hours, then covering them with 

 sea water and admitting light. It should be noted here that 

 C. tuderndatus is an animal nicely fitted for observations of- 

 this kind, because the differential pinkish tint of the soft tissues 

 of the females permits the quick and accurate identification of 



In May, a month before rii)e eggs are seen, it was noticed 

 that when sperm diffusing from a male, in a glass dish, was 

 taken up between the ctenidia of a female, it issued from the 

 posterior ends of the ctenidial channels in an altered state, for 

 the sperm-stream was then seen to contain numerous aggluti- 

 nated masses of active sperms, which persisted in sea water for 

 at least half an hour. 



During natural fecundation, however, no sperm-balls are 

 formed. The thick glutinous stream of spermatozoa passes 

 under the girdle of a female, is somewhat diluted with sea water 



3 That the discharge of sperm is under nervous control is indicated by the 



Jour. Gen. Physiol., Vol. 2, pp. 627-634). 



* See Crozier, W. J., 1920, "Sex-correlated Coloration in Chiton," Amer. 

 Nat., Vol. 54, pp. 84-88. Tidal, or rather lunar, periodicity in the libera- 



probable lunar periodicity in this genus, in 1919, at Woods Hole, and 



Biol Bull., Vol. 42, pp. 234-256. 



