454 



V. A. I'OTTS. 



these latter are developed, is sliowii in Text-fig. 6. The 

 proximal part ot" the vas deferens leading into the cloaca does 

 not appear to be yet fully formed. The cloaca is spacious, 

 and is produced on its dorsal surface into a pair of definite 

 pouches in which the chitinous copulatory spicules are formed 

 at the time of the last moult. 



Text-fio. 6. 



vas def 



cloaca 



■ intestine 



The history of the cultures may be divided into alternating 

 periods, which are distinguished respectively by the frequent 

 occurrence of males and their entire absence. During the 

 first six generations, while these experiments were being 

 prosecuted in Norfolk, the percentage of males was often 

 quite high in batches of twenty or thirty eggs, and the off- 

 spring of the majority of individuals contained at least one or 

 two. In addition, the total number of eggs laid by each 

 parent seldom exceeded 130 (150 in one case), and the 

 spermatozoa were not exhausted before death. The seventh 

 and eighth generations were reared away from a laboratory, 



