RECORDS. 



375 



Fig. 2. — Diagram of protoplasmic zones and their distribution at the first 

 cleavage in different forms. A, immature egg, assumed to have no definite segrega- 

 tion of protoplasmic stuffs. B, mature egg, with protoplasmic zones of horizontal 

 stratification. C, first cleavage, division of the chromosomes. D, E, 1% different 

 types of two-cell stage. D, Dentalium type, the lower zone isolated in one cell. 

 E, Aiiiphioxiis, nemertine, or echinoderm type ; equal division of the zones. /', 

 hypothetical type with complete separation of two zones at the first cleavage. 



