240 HARLEY N. GOULD 



are adult sperm in the vesicle. The testes of these specimens 

 however, plainly exhibit great activity, having all stages of 

 spermatogenesis to spermatocytes in one case, spermatids in the 

 other. Similar conditions are seen in two specimens of F. 

 By this time the large animals about which the smaller are clus- 

 tered are no longer males. Sections through the gonads of sev- 

 eral showed that there was no longer a testis, but no sign of 

 femaleness had yet appeared. Eventually, the large specimens 

 gradually assumed the female condition, gro\ving rapidly as 

 they did so, and the smaller individuals clustered about and 

 upon them were then nearly all found to be in the active male 

 condition (H and I) . All the small males which had gone through 

 a period of degeneration subsequently experienced regeneration 

 and finally show no sign of the former cessation of activity. It 

 is possible that some males have not degenerated at all, since 

 every lot taken showed at least one individual with normal 

 testis. 



Summing up the facts gained in this experiment: 1) Large 

 males will have an effect on the smaller ones similar to the effect 

 of large females on males, but not so marked. 2) A large ani- 

 mal with a degenerate testis will also give a stimulus to a smaller 

 individual. 3) An immature female, which was formerly a 

 male, will likewise give a stimulus. 4) After the degeneration 

 of the testis, a specimen may subsequently regenerate it again, 

 if it receives a stimulus from a larger individual. 5) The largest 

 individual in such an artificial colony as has been described never 

 shows regeneration of the testis following degeneration; there is 

 no indication that a smaller animal can affect a larger. 



Some attempt has been made to find whether a male freshly 

 removed from a normal colony will cause male development in a 

 smaller neuter; the evidence is incomplete, but suggests that it 

 may do so. 



REVERSIBILITY OF FEMALE DIFFERENTIATION 



Although an adult or nearly adult female can apparently not 

 again assume the male condition, it is clearly shown that the 

 partial development of the female organs may pause in its early 



