DESCRIPTION OF PLATES. 



The figures were drawn with the aid of the Zeiss-Abbe drawing camera, No. iii. Figs. 1-46 were 

 drawn with a Leitz oil immersion obj. t2 and a Zeiss compensating oc. 12, Figs. 47-313 with a Zeiss apo- 

 chromatic oil immersion obj. 2 mm., oc. 12. They have been reduced one-third, giving a magnification 

 of about 1000 diameters. 



Abbreviations Used on Plates 

 a\ and 02= one pair of spermatogonial chromosomes. 



a = a bivalent primary spermatocyte chromosome representing a\ and ai. 

 h\ and 62= one pair of spermatogonial chromosomes. 



b = a. bivalent primary spermatocyte chromosome representing iiand 60. 

 nil and nio = a pair of m-chromosomes. 

 n = chromatin nucleolus. 

 p, p\, p2= plasmosomes. 



-v = odd chromosome. 



