10 HARLEY N. GOULD 



edly been passing through the transition from male to female 

 while the yomiger members were successively adding themselves 

 to the chain. Orton found that in going from the male end of 

 the chain to the female end there was a "transitional series 

 from maleness to femaleness, both in primary and secondary 

 sexual characteristics." 



Orton believes that as C. fornicata grows older it gradually 

 loses the power of attaching itself after being accidentally de- 

 tached; that the foot muscles cannot relax and grasp a new sur- 

 face after a certain age. Many observations have convinced 

 the writer that the only difficulty in the way of re-affixation is 

 the shape of the shell which has been deposited by the old 

 specimens'; if the edges of the shell are trimmed away, the 

 animals will re-attach themselves and move about. 



F. Genital organs of the Calyptraeidae 



It will be of advantage to have a brief sketch of the anatomy 

 of the reproductive organs in the Calyptraeidae. Reference 

 should be made to the recent work of Scheidig ('13), Kleinen- 

 steuber ('13) and Giese ('15) as well as from the early researches 

 of Haller ('92) and Plate ('94). 



The gonad is a yellow or brown organ of an irregular, lobu- 

 lated shape lying along the intestine and between the liver lobes 

 in the short visceral sac. It may be relatively compact as fig- 

 ured by Giese for Calyptraea or it may be very diffuse, the lob- 

 ules long and widely separated from one another, as in Crepi- 

 dula plana. Anteriorly the gonad narrows down to form the 

 duct. The latter is strikingly different in the male and the 

 female phase. 



In the male condition the proximal part of the goniduct is 

 very much widened and twisted upon itself to make a convo- 

 luted seminal vesicle, for the storage of sperm. It is continued 

 anteriorly into a much narrower, ciliated vas deferens which 

 opens into the mantle cavity in the region of the shell muscle. 

 From this opening a cifiated sperm groove runs forward along 

 the right side of the neck until it reaches the large muscular penis 

 just behind the base of the right tentacle. The groove is con- 



