STUDIES ON SEX IN CREPIDULA 115 



Gonad: In three cases there were a few spermatogonia in the 

 sex gland; one at twenty-two days, one at twenty-four days, and 

 one at forty-three days. None of these corresponded with any 

 one of the three having a rudimentary penis. In sixteen cases 

 the gonad was inactive (containing only primordial male and 

 female cells). The remaining five were the animals sectioned 

 after fifty days' isolation. They had passed from the neuter to 

 the incipient female condition, having various stages in early 

 growth periods of oocytes, and had grown considerably in size, 

 being now from 14 to 23 mm. in length. 



A similar record was made of males removed from colonies 

 and kept isolated in vials. As was shown in a former paper, all 

 males lose their male characters after removal from the colonies. 

 Four samples were taken from the vials after thirty-six days, 

 four after forty-six days, four after fifty-three days, and four 

 after sixty days. There was no resumption of spermatogenesis 

 or redevelopment of external male organs after the degeneration 

 in any case. The only hint of any such activity was the presence 

 of a few dividing spermatogonia in the gonad of one isolated 

 forty-six days. It should be recalled that previous experiments 

 demonstrated the ability of degenerate males to reassume the 

 functional male state under stimulus from larger individuals. 



It is thus indicated that the gonads of isolated small specimens 

 may produce a few spermatogonia, but proceed no further toward 

 spermatogenesis; and the spermatogonia so formed later degener- 

 ate, as sections show. The isolation experiment is meant to clear 

 the way for others, i.e., to show, in cases where partial male de- 

 velopment is induced under weak stimulus, how much of this is 

 due to internal causes. The writer concludes that rapid sperma- 

 togonial multiplication, formation of spermatocytes, or any 

 later stage of spermatogenesis is an indication of an external 

 stimulus. 



In previous experiments where they developed male charac- 

 ters under observation, the neuters were placed as closely as 

 possible to the larger animals. Only in this way could the stimu- 

 lus be clearly shown. The writer failed to find positive evidence 



