ül2 I. IKEDA : 



the sexual orn-aus lie grouped together, a, uumljer of large eggs 

 are fre<|uently tbuud, Hoatiug freely iu the eoelouiic fluid of the 

 l)ody-eavities. These eggs do not differ in any res])ect from those 

 in thi' ncphiidial region as regards tlie size, the appearance of 

 the karyokinetie Jigure, or the nunil)er of chi'oniosonies. 



The facts aI)ove stated plainly point to the followijig con- 

 clusion : — Tlie oo(joiii<i fall into lite body-car it ics by a dehiscence of 

 the ovarian vjalU and Jiere derclop until they reach the stage of 

 primary oocytes. These travel yradually upwards to the nephridial 

 region, retaining memiwhile the nuclear figure formed for the 

 production of the first polar globule. Reaching that region, the 

 primary oocytes are destined sooner or later to be carried by way 

 of the nephj'idia to the exterior, where tJicy become fertilized by 

 spermatozoa from oilier individuals. 



Keserving an account of the s})ermatogenesis and ovogenesis 

 lor a future occasion, I may here refer t(j a few facts observed 

 by me relative to the process of fertilization. AVhen the two 

 sexual elements arc ai'tiiicially brought togethe]', numl)erless sper- 

 matozoa soon attach themselves to the surface of the ovum. About 

 10 minutes afterwards, the lii'st })olar globule makes its appear- 

 ance, followed soon afterwards by the second, ^[eanwdiile a small 

 clear spot, probably marking the place where the male element has 

 entered, ap])ears on the surface of the egg ; it is however ol)serv- 

 al)le for only a very short time. Both ligs. 1*.' and 20 are 

 sections of ova taken from the emlnyonal mass. The ovum given 

 in fig. 19 is fully mature and ready to l)e fertilized ; close to the 

 j)olar globules vests the large female pronucleus. The ovum 

 re})resented in fig. 20 belongs to a stage of fertilization in which 

 the two ]ironuclei stand closely side by side. The larger female 

 ])ronucleus has a nuclear meml)rane irregular in contour. The 



