A study of the Chromosomes in three species of Pseudococcus. 
59 
"Wliatever the significance of the features of these two types of reduc- 
tion may be, a superficial resemblance can not fail to be recognized. In 
both the spindle fibers connecting the chromosomes with one pole are 
perfectly normal. In both the rest of the spindle is not completed or 
at least is only irregularly formed. In Hymenoptera the absence of one 
set of chromosomes may fully account for such irregularity, but in Pseudo- 
coccus a set of chromosomes is available for distribution to each pole. 
Purely by analogy then, it may be assumed that the chromosomes con- 
nected with the irregulär fibers — the loose group — lack certain proper- 
ties which would make them equivalent to the massed group. Whether 
this lack is indicative of a loss and whether this loose group is on its way 
to disappearance must be left to further investigation. If either of these 
surmises be correct, the origin of haploid males is near to solution. In 
this Connection it may not be amiss to recall that at least one species 
with haploid males occurs among the Homoptera (Trialeurodes, Schrä- 
der, ’20) — the Order of which Pseudococcus is a member. 
In conclusion I would like to point out that since in the female there 
are evidently five pairs of homologous chromosomes as shown by the 
formation of five tetrads, and in the male five chromosomes remain in 
distinct isolation from the other five throughout the prophases, — there 
is no doubt that the female of Pseudococcus is homozygous and the male 
heterozygous for sex. 
Summary. 
1. In the prophases of the first spermatocytes of Pseudococcus citri, 
P. maritimus, and P. nipae, five chromosomes are evolved considerably 
in advance of the remaining five chromosomes. 
2. The chromosomes first evolved have a tendency to clump in case 
of P. maritimus and P. nipae. This tendency is less marked and occa- 
sionally absent in P. citri. 
3. The first spermatocyte division is equational and ten chromosomes 
go to each pole. There is evidence that the grouping of the chromosomes 
previously observed, persists in the daughter cells. 
4. The second spermatocyte division follows seemingly without a 
regulär interkinesis. Apparently the five clumped chromosomes go to 
one pole, and the remaining five to the other pole. This is the reduction 
division. 
5. The distribution of the chromosomes in the reduction is not 
accompanied by a cytoplasmic division. Each cell is a double sperma- 
tid which- gives rise to two spermatozoa. 
