174 VICTOR E. EMMEL 



Third, considerable evidence has accumulated demonstrating 

 that the erythrocytic nuclei may, while still within the erythro- 

 blasts, undergo in some cases a process of fragmentation or bud- 

 ding off of one or more nuclear particles, as described for example 

 by Howell ('91) in the cat after hemorrhage. Nuclear particles 

 occasionally found in plastids have accordingly been explained 

 by various investigators, including Howell ('91), Weidenreich 

 ('04, '06), and Jolly ('07), as nuclear fragments remaining after 

 the expulsion of a part of the nucleus and their presence has 

 consequently been regarded as an argument for nuclear extrusion. 

 On the other hand, Pappenheim ('95) among others, has utilized 

 these particles as evidence for intra-cellular nuclear disintegra- 

 tion rather than for extrusion. However, here again it may be 

 questioned whether this datum can be considered conclusive for 

 either view, for a third possibility remains concerning these 

 particles, namely, that in case a portion of the nuclear material 

 had budded off from the erythroblast nucleus, subsequent divi- 

 sion of the cell into two parts by a process of cytoplasmic con- 

 striction may take place in such manner as to include the nuclear 

 particle in the newly formed plastid and thus account for the 

 origin of non-nucleated erythrocytes containing remnants of 

 nuclear material. In the pig embryo, at least according to the 

 present observations, these nuclear particles are of infrequent 

 occurrence and no plastids containing such particles were observed 

 in the cultures. In triton, however, Jolly ('07) describes an 

 authentic case of the formation of a nuclear bud in the nucleated 

 red blood corpuscle and the inclusion of this nuclear fragment 

 in a portion of the cytoplasm subsequently constricted off from 

 the nucleated cell which he describes as follows: 



On peut observer des fragments spheriques contenant un corps color- 

 able par les coleurs basiques; ce corpuscle est a fragment nucleaire, un 

 bourgeon nucleaire qui s'est isole efc qui s'est trouve separe de la cellule 

 avec le fragment. II ne s' agit pas la d'alterations artificielles dues aux 

 reactifs;lephenomene peut etre observe sans le secours de reactifs (p. 195). 



The indirect evidence for nuclear extrusion just considered, 

 then, is of such a character that for a final solution of the problem 

 it appears that recourse must be made to the direct evidence for the 

 actual process of enucleation as drawn from the study of fixed 



