DURATION OF EMBRYO DEVELOPMENT. 37 



and a vitelline membrane but little removed from it. A 

 large amount of water was absorbed, and the vitelline 

 membrane was continually distended, until at last it 

 readied the proportions represented in Fig. 1. The yolk 

 presented itself, by transmitted light, as a quite dark 

 homogeneous round body, which on nearer examina- 

 tion, and when pressed, consisted of an absolutely 

 transparent plasma and very fine fat globules. The 

 diameter of the egg was not more than O105 

 mm. I could not find a nucleus in the fertilized 

 eggs, although in the unfertilized, taken from the 

 ovary, it was always quite plainly to be seen. I do 

 not however at all mean to say that the nucleus 

 vanishes ; I know the difficulties in the wa}^ of finding 

 it in the fertilized egg." 



These statements I can for the most part confirm. 

 In certain points however I went further than 

 Kowalevsky. These mainly are concerned with the 

 observation of a polar body, and in close connection 

 therewith the proof of the polar differentiation in the 



unsegmented egg. 



The first processes of development which I brought 



within the sphere of my examination, have to do with 

 the eggs just ejected, so far as they were liberated by 



