256 KANSAS UNIVERSITY SCIENCE BULLETIN. 



peared from the ectoderm, without any marked change in the 

 total number. The fact that in the two buds, 3 and 4, no 

 germ cells have migrated into the "glockenkern" probably 

 indicates nothing more than an individual variation in the 

 form of a delayed migration. 



Table V. — Number of Germ Cells in Stage E Buds. 



, -Entoderm.- , Total "(ilocken- 



Bud. Sex. Prox. Cent. Dist. entoderm. Ectoderm. kern." Total. 



1 Male 3 3 .. 25 28 



2 Female 1 2 3 2 22 27 



3 Male 1 3 4 .. 19 23 



4 Male . . 32 32 



5 Male 1 . . 1 . . 25 26 



6 Male 2 7 9 2 13 24 



In stage E, shown in Table V, a large majority of the germ 

 cells, and in some cases practically all of the germ cells, have 

 passed into the "glockenkern." The germ cells still in the 

 entoderm are in a position to migrate later into the "glocken- 

 kern" and will probably do so. 



4. — Multiplication of germ cells and sexual differ entiatioyi. 

 Throughout the development of the medusae thus far there has 

 been no apparent increase in the total number of germ cells, 

 and no visible sexual differentiation. After stage A there is 

 a multiplication of germ cells in the "glockenkern" and a dif- 

 ferentiation of the cells into eggs and sperm in the different 

 medusae. 



The egg cells increase enormously in size, the cytoplasm be- 

 comes somewhat vacuolated and yolk granules are deposited 

 in it. There is no indication of the actual engulfment of one 

 cell by another, nor the absorption of disintegrating cells by 

 others (figure 10). 



In older male medusae, the number of sperm is considerably 

 greater than the number of eggs in the manubrium of female 

 medusae of corresponding size. The complete process of sper- 

 matogenesis can be observed in a single bud (figure 11) . The 

 germ cells are rapidly dividing in the region near the ento- 

 derm, and later stages are seen near the periphery. The proc- 

 ess of differentiation results in a condensation of cytoplasm 

 and nucleus, forming an almost spherical dark body, the 

 sperm. No attempt was made to follow the details of this 

 process. 



