22 SEGMENTATION. 



remnant of the old nucleus in the cases described is nothing 

 more than its membrane, no difficulty is offered to the view 

 that the constituents of the old nucleus may help to form tho 

 new ones. 



In many cases the total bulk of the new nuclei is greater 

 than that of the old one; in such instances part of the proto- 

 plasm of the cell necessarily has a share in forming the new 

 nuclei. 



Although, in instances where the nucleus vanishes, an abso- 

 lute demonstration of the formation of the fresh nuclei from the 

 matter of the old one is not possible; yet, if cases of the division 

 of the old nucleus to form the new ones be admitted to exist, 

 the derivation in the first process of the fresh nuclei from the 

 old ones must be postulated in order to maintain a continuity 

 between the two processes of formation; and, as I have at- 

 tempted to shew, all the circumstantial evidence is in favour of it. 



Admitting the existence of the two extreme processes of nu- 

 clear formation, I wish to shew that my results in Elasmobranchs 

 tend to demonstrate the existence of intermediate steps be- 

 tween them. The first figures I described of two opposed cones, 

 appear to me almost certainly to represent nuclei in the act of 

 dissolution; but though a portion of the nucleus may stream 

 out into the yolk, I think it impossible that the whole of it 

 does\ 



I described these bodies in two states. An earlier one, in 

 which the two cones were separated by an irregular row of 

 deeply stained granules ; and a later one in which a furrow had 

 already appeared dividing the cones as well as the cell. In 

 neither of these conditions could I see any signs of the body 

 vanishing completely. It was as clearly defined and as deeply 

 stained as an ordinary nucleus, and in its later condition the 

 signs of the streaming out of material from its pointed extremi- 

 ties were less marked than in the earlier stage. 



All these facts, to my mind, point to the view that 

 these cone-like bodies do not disappear, but form the basis 

 for the new nuclei. Possibly the body visible in each cone 



1 After Strcasburger's obsei-vation it must be considered very doubtful whether 

 the streaming out of the contents of the inicleus, in the manner implied in the 

 text, really takes place. 



