On the Dimegalous Speim and Chromosomal Variation of Euschistus, etc. 135 
ln the first spermatocytes in 67 out of 98 cases, there are 8 sepa- 
rated elements all of which divide (figs. 40, 41), the smaUest of them being 
the smaller diplosome (d). These are similar to the normal cases of the 
other testes described. But the following abnormalities were found: 
1. 8 larger elements in addition to the smaller diplosome, giving a 
total of 9, but 110 small siipernumerary elements. Such cases are shown 
in figs. 42 — 44. They differ from the normal in having a pair, s, of equal 
volume, always placed near each other and usually in the centre of the 
spindle. Such cases are precisely like the exceptional ones of testis no. 282, 
and that these s-chromosomes divide is well shown in the case of fig. 43. 
2. In addition to the 8 normal elements there may be present 1 or 2, 
never morej supernumerary small elements, giving a total of either 9 or 
10. These supernnmeraries are lettered x in figs. 45 — 47, PI. X (none of 
which Show the total number of chromosomes) and fig. 49. When 2 occiir 
they ai-e of approximately equal size, they generally appear slightly larger 
than the smaller diplosome (d) and may be distinguished from it by the 
fact that they are not bipartite. These supernnmeraries are marked by 
constancies of size and form. When only one is seen it is probable the 
other is not absent but hidden behind another chromosome. It is on 
account of the occasional presence of 2 of these that I suggested some 
spermatogonia niight contain 16 separate elements. They are not always 
but sometimes attached to a larger chromosome, as evidenced in figs. 45 — 47 
and their attachment to one end of a larger chromosome is the more 
usual, while the smaller diplosome never holds such a position in this 
Stage. Sometimes both are nearer one spindle pole than the other 
(fig. 47). It would seem that they do not divide in this mitosis since 
they never appear bipartite. 
3. There may be combinations of the two preceding variations, 
presenting a total of either 10 or 11 elements. Thus there may be 2 s-chro- 
mosomes (s, fig. 51) and 1 supernumerary (a;), or 2 s-chromosomes and 
2 snpernumerarles (fig. 48, 50). 
(’hromosomes were counted in 147 second spermatocytes. 138 of 
these showed the normal condition of a bivalent diplosome and 6 peri- 
pheral autosomes (fig. 52). In some cases it is probable, on the reaso- 
ning employed for testis no. 282, that one of these autosomes may be a 
bivalent formed by the conjugation of the 2 s-chromosomes. One case 
exhibited only 6 separate elements, possibly due to the 7th being hidden 
beneath another. Six cases exhibited the following variations: 1. No 
supernumerary element, but the s-chromosomes separated (fig. 53), ma- 
king a total of 8. 2. The normal condition with the addition of 1 super- 
