118 HARLEY N. GOULD 



Female development is much slower than male, and it is likely 

 that the most of these animals were already in the course of fe- 

 male differentiation when selected as neuters. The percentage 

 of 'inactives' is also greater among the larger specimens. It has 

 been evident to the writer from many observations that the tend- 

 ency to male development under stimulus gradually wanes as 

 the period approaches when female development may set in. 

 It is, however, sometimes possible to superimpose male on early 

 female development, as shown in the former paper. 



In the watch-crystal experiment forty-three animals out of a 

 possible sixty-seven showed some degree of male activity in the 

 sex gland, twenty-five of them being fully developed males. 

 Compare this with the result obtained when neuters were placed 

 on and closely around females. In the latter case (from records 

 in previous paper) fifty-one out of a possible fifty-three showed 

 some degree of male development, and thirty-four of them were 

 adult males. It is clear that more males develop when the 

 neuters are close to the source of the stimulus than when sep- 

 arated by several millimeters ; and furthermore, the difference in 

 the results of these two experiments cannot be adequately set 

 forth in tabular form. Examination of the gonad under the mi- 

 croscope shows it more strikingly. Many marked 'adult testis' in 

 specimens from the watch-crystal experiment are only a fraction 

 of the size of the gonads developed in those placed close to or on 

 the large females. There are often signs of arrested development 

 in the former, shown by the paucity or absence of some stages of 

 spermatogenesis. 



An examination of the small individuals in a large number of 

 normal colonies shows about 62 per cent adult males (determined 

 from external characters). By placing neuters on and close to 

 females, about the same percentage of adult males was obtained, 

 and this could have been raised considerably by rejecting all 

 those specimens which had moved several millimeters from the 

 females during the course of the experiment. In the watch- 

 crystal experiment only about 38 per cent became adult males. 



The development of the male phase by neuters imprisoned in 

 depression slides thus shows that the male-producing stimulus is 



