ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 279 
idiozome substance commences to disperse over the surface of the nucleus. 
In this stage and in the post synapsis, large groups of cell syncytia are 
found, which are characterised by a large quantity of yolk, and by 
absence of demarcating cell-membranes ; these syncytia denote groups of 
cells which have received an especially abundant nutritive supply ; they 
divide into smaller groups of two or three cells each, before the rest 
stage, the latter cells developing quite normally. 
Of the six follicles in the testes two contain spermatocytes of about 
double the size of those in the other follicles, the larger size being due 
to greater increase in the amount of the cytoplasm, idiozome substance, 
and nuclear sap ; in both large and small spermatocytes there are the 
same processes of reduction division. 
The first spermatocytes attain their greatest size in the rest stage : 
the growth period extends from the synapsis to the rest stage. In the 
prophase of the first reduction, the chromatin reticulum shortens and 
condenses into 3-6 long loops ; these shorten and thicken, and become 
dumbbell-shaped. They and the chromatin nucleolus are eventually trans- 
versely halved. In the second spermatocytic mitosis the seven chromo- 
somes and the chromatin nucleolus again exhibit a transverse division. As 
to peculiarities of the spermatogenesis in Pentatoma , the following may 
be emphasised. There are 14 chromosomes in the spermatogonia ; in the 
synapsis of the first spermatocytes one of these becomes differentiated 
into the chromatin nucleolus ; the remaining 13 are reduced to 3-6 
during the synapsis : yet in the prophase of the first reduction division, 
only so many segment transversely as to produce in all cases seven, i.e. 
exactly half the normal number. The differentiation of a chromosome 
into the chromatin nucleolus is another peculiarity, and so is the occur- 
rence of large and small spermatocytes. 
Montgomery’s observations furnish no strict proof of the permanence 
of the centrosomes. The idiozome apparently takes no part in the for- 
mation of spindle-fibres. Since it increases in amount, especially in the 
growth period of the spermatocytes, and is more voluminous in cells of 
the large generation, it might represent some metabolic substance con- 
nected with processes of nutrition ; but if this were the case, since the 
centrosomes lie within it, the latter might be considered to be agents in 
the process of nutrition, as well as being the chief mechanical centres in 
mitosis. In his general considerations, the author gives most attention 
to the question — what is a chromosome. 
5. Arachnida. 
Eyes of Spiders.* — Herr E. Hentschel has studied the structure and 
development of the eyes in various spiders, — species of Tarantula , Ly- 
cosa , Attus, &c. Following Bertkau, he distinguishes the anterior inner 
pair of eyes from the three other pairs, under the titles Hauptaugen and 
Nebenaugen respectively. It must not be supposed, however, that the 
latter are biologically of less value than the former. The most important 
conclusions are the following : — 
(1) In both types of eyes the nerve-fibres unite with the nucleus- 
bearing ends of the retina-cells, while the rod-bearing ends are free. 
* Zool. Jahrb. (Abth. Anat.), xii. (1899) pp. 509-34 (2 pis.). 
