458 WINTERTON C. CURTIS, 



and following this the appearance of a cavity (PI. 31, Fig. 2 te 3) 

 which increases in size as the cells are spread out in a thin epi- 

 thelium until in a fully formed active follicle the cavity is almost full 

 of daughter cells spermatids and a fev/ fully formed spermatozoa {te ^), 

 are the same as described for other Planaria. In worms taken during 

 the last few days of October the majority of the follicles were well 

 formed and early stages were no more numerous than at a later date. 

 As Spring approached only a few were found where the sperm-mother 

 cells seemed to have passed their period of greatest activity and to be 

 no longer dividing. It must be said therefore that there has been a 

 slow production of spermatozoa all the Winter and that the condition 

 of the testes remains about the same during the period. 



The central cavity of each follicle is usually filled with daughter 

 cells, developing spermatids and a few adult spermatozoa. The sper- 

 matozoa are frequently met with in the testicular canals (PI. 31, 

 Fig. 2 spz), everywhere in the vasa deferentia (Figs. 5 and 6), and 

 are always collected in a closely packed mass partially filling the 

 seminal vesicles (Fig. 7 spz) to which it is evident they make their 

 way soon after reaching maturity. The vesicles did not show any 

 very decided increase in size, but in some worms taken during April 

 they were larger than at any time during the Winter. My observ- 

 ations did not extend to the Summer and I am therefore not able 

 to make any statement regarding their condition during the repro- 

 ductive season. 



Very much the same condition obtains in the female system. 

 The ovaries of every worm showed ova in many stages (PI. 31, 

 Fig. 4, and PI. 32, Figs. 9 and 11) and worms were killed in No- 

 vember with more large ova than any taken during April. The ova 

 are probably slowly growing all Winter, but as in the case of the 

 testes there is no marked change. The yolk-glands, from the con- 

 dition of scattered cells enveloped in a stroma-like supporting sub- 

 stance (PI. 32, Fig. 14), were found by the latter part of the Winter 

 to have gained considerably in bulk by an increase in the number 

 rather than in the size of their constituent cells. Evidence of their 

 rapid growth is found in the frequent occurrence of two nuclei in a 

 cell that shows no further signs of division (PI. 32, Fig. 14 yc). 



The uterus has shown no activity during the period. There is 

 no secretion from the walls apparent in its lumen and spermatozoa 

 have never been found there. Spermatozoa were found, however, in 

 every worm examined, all along the oviducts and a mass of them 



