EXPLANATION OF PLATES 



All the figures were drawn with the aid of a camera lucida, the projection 

 distance being 410 mm. Spencer 2-mm. oil-immersion objective and compensating 

 ocular X 10 were used. Magnification of 3,200 diameters. 



The following abbreviation is used: id, idiosome, the chromosome in which 

 it is a part of the chromatic body from which it is derived. 



PLATE 1 



EXPLANATIOX OP FIGURES 



1 Spermatogonium showing two unequal chromatin bodies in the nucleus. 



2 Prophase, first spermatocyte, showing two unequal chromatin bodies 

 in the nucleus. 



3 Prophase, first spermatocyte, showing formation of chromosomes and the 

 isolated position of the idiosome. 



4a Late prophase nucleus, first spermatocyte, showing nine tetrad auto- 

 somes and the isolated idiosome. 



4b Late prophase, first spermatocyte, showing idiosome attached to the 

 end of one of the nine autosomes. 



5a Polar view of metaphase plate, first spermatocyte, showing idiosome 

 attached to the end of one of the autosomes. 



5b Lateral view of metaphase plate, first spermatocyte, showing idiosome 

 attached to the end of one of the autosomes. 



5c Polar view of metaphase plate, first spermatocyte, showing idiosome 

 not attached to an autosome. 



6a Early anaphase, first spermatocyte, showing lagging division of the 

 heterochromosome. 



6b Anaphase, first spermatocyte, showing lagging of the heterochromosome. 



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