96 



bulletin: museum of comparative zoology. 



An extended study of the eliromosomes during the maturation 

 period has convinced me that every spermatocyte possesses the same 

 number of bivalent autosomes of each of the three types. This is not 

 a statement which can be easily demonstrated, since only rarely can 

 the structure of all the elements of any one cell be determined with 

 certainty. Viewed at slightly different angles the appearance of a 



M. 



NN. 



Figs. Ma, Mb, Mc. Successive sections of spermatocyte of Dissosteira Caro- 

 lina during the early anaphase of the first division. All the chromosomes 

 are shown, the monosome being at the right in Fig. Mc. X 966. 



Fig. N. — Polar view, metaphase of first maturation division of Dissosteira 

 Carolina. X 966. 



Fig. NN. — Polar view, metaphase of first maturation division of Stenobothrus 

 curtipennis. X 966. 



chromosome may vary greatly, and_ at certain angles a given chromo- 

 some may be indistinguishable from one of a different type. Polar 

 views of the equatorial plate are most favorable for identifying the 

 different forms, but even in such cases it is often impossible to be sure 

 of the structure of all the elements. However, in the most favorable 



