INDIVIDUALITY OF CHROMOSOMES. 21 



the distal pole. The spermatocytes are so small that conditions 

 there are much more difficult to decipher. Further study will 

 probably clear up this matter and reveal the method of forma- 

 tion of the various chromosomes in the growth period. 



It gives me pleasure to express my gratitude to Dr. Frank R. 

 Lillie for reading this manuscript, as well as much for helpful 

 encouragement during the progress of the work. 



HULL ZOOLOGICAL LABORATORY, 

 UNIVERSITY OF CHICAGO, 

 August 6, 1904. 



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