578 VERA DANCHAKOFF 



is surrounded at this time by a dense net of cytoplasm, often 

 intensely impregnated with chromatic substance, and after dis- 

 appearance of the membrane is in immediate contact with it. 

 All these facts suggest the idea, that the chromatin within the 

 nucleus is differentiated at least partly at the expense of the 

 basophihc substance of the cytoplasm. ^ 



Far from insisting upon identity of the chromatin within the 

 nucleus and the chromatic accumulation found in the cytoplasm 

 of immature eggs, I cannot but take into consideration their 

 intimate relations. Possibilities of interaction between the 

 basophilic chromatic substance and the cytoplasm are great 

 while the latter is transported to the nucleus. Incorporated 

 within the nucleus, this substance again may undergo chemical 

 changes. Is it bound chemically to the achromatic substance 

 of the nucleus? A definite answer to these questions is hardly 

 possible at present. The attraction of cytoplasmic chromatic 

 substance by the karyoplasm, its incorporation within the nu- 

 cleus, its further participation in the development of chromo- 

 somes — all these facts seem to inform about complex chemical 

 interchanges between the constituent parts of the cell. 



Up to the present the chromatin and especially the reproduc- 

 tive chromatin has been considered as of exclusively nuclear 

 origin. The question of chromatin synthesis has been somewhat 

 neglected. Where, and at the expense of what does chromatin 

 synthesis take place? The loss of staining capacity by the 

 chromatin in a resting nucleus has been attributed to its chem- 

 ical change. The individuality or even the immutability of 

 chromosomes has been chiefly suggested by Boveri's observations. 

 Boveri described in the resting nuclei of Ascaris eggs protuber- 

 ances, which correspond to the form of chromosomes, and found 

 that the new formed chromosomes at the next prophase appear 

 in these proturberances. 



The small achromatic female pronucleus in the sea urchin 

 eggs does not offer any evidence for the persistence of chromo- 



' I am indebted to Prof. David H. Tennent for the opportunity of studying 

 some of his preparations of different parthenogenetic sea urchin eggs. They 

 show a similar development of the first chromatin particles in the nucleus in 

 close connection with its membrane. 



