5O WILLIAM E. HOY. 



out clearly. In a few cases it is difficult to make them out, 

 owing to the fact that they lie very close to a larger chromosome. 



Of course a difference in the general size of the chromosomes as 

 a whole is to be found, and it is probable that no two groups 

 would appear exactly alike. The size of the chromosomes in the 

 metaphase groups is directly proportional to the size of the cyto- 

 plasmic body. In the metaphase groups there is a longitudinal 

 splitting of each chromosome. In no case has a transverse 

 division been observed here, nor has there been observed a doub- 

 ling in the number of chromosomes in this phase, such as Wilson 

 describes in the follicle cells. 



Diabrotica vittata. The spermatogenesis of Diabrotica vittata 

 was worked out and published in 1907 by Miss Stevens. In the 

 spermatogonial divisions she found twenty-one chromosomes of 

 various sizes and shapes. The ^-chromosome which she figures 

 is one of the medium-sized chromosomes. The other twenty 

 she was able to pair. In the second spermatocytic division the 

 x-chromosome appears as a more or less rounded body, which 

 passes undivided to one of the poles of the spindle. There are 

 no such clear cut size differences as are found in Anasa. 



The results which I have obtained from a study of the eggs 

 and early embryos of Diabrotica, though somewhat meager it is 

 true, clearly support the same conclusion as was reached in the 

 case of Anasa, namely that the embryos are of two classes, one 

 having twenty-one, and the other twenty-two chromosomes in 

 all the mitoses. 



Some clear cut figures were obtained in the maturation of the 

 egg. The anaphase of the first maturation division revealed 

 eleven dyads. These in turn divided, leaving eleven monads in 

 the fully matured egg. This brings the maturation of the egg of 

 Diabrotica into line with that described for other insects. 



In conclusion it may be said that in neither Anasa nor Dia- 

 brotica were there any numerical differences between the gonial 

 and the somatic chromosomes, such as have been described in the 

 rabbit by Winiwarther, and more recently, in man by Wieman, in 

 Osmia cornuta by Armbruster, and in Diaptomns by Krimmel. 



