INDIVIDUALITY OF THE GERM-NUCLEI. 267 



double. The genetic continuity of each half of the double 

 nucleus has been clearly traced to an advanced cleavage stage. 



During late cleavage and in the early gastrula the nuclei are 

 still typically double, but certain irregularities which tend to 

 disguise the double structure occur with increasing frequency 

 and the segregation of maternal and paternal chromatin cannot 

 always be demonstrated. 



The hypothesis of individuality of the germ -nuclei as applied 

 to those species in which there is a mingling of maternal and 

 paternal chromosomes is discussed, and supported by considera- 

 tions regarding the persistent individuality of the chromosomes. 



ZOOLOGICAL LABORATORY, 



MICHIGAN STATE NORMAL COLLEGE, 

 YPSILANTI. 



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