172 VICTOR E. EMMEL 



persist, grow and again participate in the formation of new plas- 

 tids, whether they may possibly become cells of a lymphocytic 

 type, or whether, as is in accord with the more generally accepted 

 view, they are in the last stages of a cytomorphosis, which is soon 

 to culminate in their death and disappearance. While the latter 

 alternative seems at present the more probable, the force of one of 

 the usual arguments supporting it based upon the reduced size 

 and compactness of the nucleus appears less convincing, so far as 

 this nuclear condition is concerned, if one considers that in the 

 cytomorphosis of the spermatocyte the small compact nucleus of 

 the spermatid, together with the reduced amount of cytoplasm 

 remaining at the end of the process is by no means indicative of 

 ensuing deterioration and cell death. 



In conclusion, then, concerning the erythrocytes of the pig em- 

 bryo, the occurrence in carefully fixed vessels of erythroblasts 

 having a constriction of the cytoplasm between the nuclear and 

 cytoplasmic poles of the cell, the variation in the size and form 

 of the plastids, the presence of pyknotic erythrocytic nuclei sur- 

 rounded by a rim of hemoglobin-containing cytoplasm, and the 

 observation in fresh vessels of the separation off of a cytoplasmic 

 part of the erythroblast by a process of cell constriction, is evi- 

 dence strongly indicating the origin of plastids within the circu- 

 latory system of the embryo by a process of cytoplasmic constric- 

 tion similar to that observed in the cultures. 



DISCUSSION CONCERNING THE ORIGIN OF NON-NUCLEATED 

 ERYTHROCYTES 



1. THE QUESTION OF NUCLEAR EXTRUSION AND INTRACELLULAR 



DISINTEGRATION 



As is well known there are two prevalent views concerning the 

 enucleation of the mammalian erythroblast. The one, which 

 traces its origin to Kolliker ('46) being that in the transformation 

 of erythroblasts into non-nucleated corpuscles the nucleus is dis- 

 solved within the cell, the other, originating with Rindfleisch ('80) 

 that the nucleus is expelled from the cell. In spite of the subse- 

 quent accumulation of an extensive literature for both these 

 views, in the words of Lazarus and Naegeli ('09) in Erlich's work 



