STUDIES ON SEX IN CREPIDULA 17 



of the primordial egg cells. If there are cells with a nutritive 

 function they must be those of the syncytial layer. As has been 

 said, the follicular cells have not been seen to divide by mitosis, 

 at any period. The fact of amitotic division is hard to estab- 

 lish; but some indications of it have been seen, and it has been 

 described in the follicle cells of the gonads of other and widely 

 separated groups of animals. 



Male development 



Let us now return to a consideration of the general develop- 

 ment of the young gonad. In the postlarval stage there may 

 (fig. 3) or may not (fig. 2) be a small lumen in the rudimentary 

 sex gland. The presence of a few spermatogonia in the lumen 

 is not a sure sign that male development is about to take place. 

 The free cells may remain inactive and degenerate, giving rise 

 to homogeneously staining bodies such as appear in figure 1. 

 The gonad shown in figure 1 is that of a more minute specimen 

 than those shown in figures 2 and 3, yet spermatogonial cells 

 have already been formed and cut off into the interior, and sub- 

 sequently died instead of continuing their development, as their 

 irregular shapes and homogeneous stain give evidence. 



With further growth of the young Crepidula the gonad be- 

 comes enlarged and more irregular in shape. Processes are put 

 out. These are not constant in number or direction; for the 

 shape of the gonad depends upon the spaces which it may oc- 

 cupy between the lobes of the digestive gland or between the 

 digestive gland and the intestine, and in different specimens the 

 condition of the digestive gland and the amount of distention 

 of the alim.entary tract vary. One arm of the gonad usually 

 grows to the left and downward, following the outline of the in- 

 testine. This seems to be the first direction of growth, and the 

 process so formed sometimes becomes temporarily larger than 

 the central part of the gonad. Growth also goes on posteriorly. 

 The arm which reaches to the right and forward to join the 

 goniduct becomes drawn out to considerable length, even into a 

 tube or strand as small as the duct itself; yet readily distin- 

 guishable from it by the structure of its cells. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 23, NO. 1 



