242 HARLEY N. GOULD 



male cells were also lacking. If they completely disappear, as 

 seems to be the case, the inability of females to re-assume the 

 male phase is explained. 



NATURE OF THE STIMULUS 



As soon as it became evident that there was actually a stimu- 

 lus passing from the larger to the smaller individuals of C. plana, 

 affecting the sexual development of the latter, experiments were 

 undertaken to discover the nature of that stimulus. Unfortu- 

 nately up to this time all experiments have given negative re- 

 sults. Yet since they have served to limit the field of inquiry 

 and furnish additional proof of the presence of the unique influ- 

 ence, it is thought worth while to include them in this report. 

 Other more precise tests are planned for the future. 



Copulation 



When it was first found that males would degenerate on being 

 removed from the vicinity of the females it was suggested that 

 the sex gland atrophied through loss of functional activity; 

 but the development of male organs in neuter animals which 

 had not previously the power of copulation disposed of this 

 possibility. 



Motility j 



Males are more motile than females (Conklin, '98) or than 

 sexually inactive individuals. Is it possible that frequent 

 movement of small animals in large colonies has anything to do 

 with development of male organs? To this it may be answered 

 that motility is not necessarily a property of males; a consider- 

 able number of males have been found whose shells indicated by 

 the conformation to the underlying surface that they had not 

 moved at all during nearly the whole period of their lives; and 

 one neuter animal remained constantly in the same spot for 

 several weeks while undergoing male development under ex- 

 perimental conditions. 



