STUDIES ON CHROMOSOMES ie 
DESCRIPTIVE 
Since the two species agree very closely save in respect to the 
idiochromosomes they may conveniently be considered together. 
Before describing the divisions, attention may be called to a 
striking difference between the two species in respect to the size 
of the cells and karyokinetic figures. As a comparison of the 
figures will show, the spermatocytes and maturation division- 
figures of N. hilaris are much Jarger than those of N. viridula. 
In the spermatogonia this difference is also apparent, though less 
marked. In the ovaries, strange to say, it cannot certainly be 
detected, either in the dividing cells or in the nuclei of the follicle- 
cells or of the tip-cells at the upper end of the ovary. It would be 
interesting to make a more accurate study of these relations; 
but I will here only state that the differences between the two 
species seem to arise mainly through greater growth of the 
spermatocytes in N. hilaris. With this is correlated a greater 
size of the testis as a whole; but the size of the entire body in this 
species is but little larger, as far as I have observed, than in N. 
viridula. 
As regards the general features of the divisions, the diploid 
groups of both sexes uniformly contain fourteen chromosomes, 
the first spermatocyte-division eight and the second seven, the 
idiochromosomes being, as is the rule in Hemiptera, separate and 
univalent in the first division. 
1. The second spermatocyte-division 
a. The idiochromosomes. Polar views of the second division 
always show 7 chromosomes which are usually grouped in an 
irregular ring of six with the seventh near its center (fig. 3 j—m, 
figs. 14, 15). In both species one chromosome of the outer ring 
(s) can usually be distinguished as the smallest, though this is 
not always evident owing to the apparent variations produced 
by different degrees of elongation. This is the chromosome that 
I formerly supposed to be the idiochromosome-bivalent, despite © 
its peripheral position, and despite the fact, which I had myself 
described, that a similar small chromosome, also peripheral in posi- 
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JOURNAL OF MORPHOLOGY, VOL. 22, No. 1 
