In _Aphrophora_ the follicles of each testis are free, forming a dense
cluster, each follicle being connected with the vas deferens by a short
duct. The very young follicles are spherical, the older ones ovoid in
form. The primary spermatogonia (plate XIV, fig. 237)--very clear cells
with a lobed nucleus which stains slightly--occupy the tip of the
follicle. Next to these comes a layer of cysts of secondary
spermatogonia which are conspicuous for their deeper staining quality
(fig. 238). There appears to be no plasmosome in either class of
spermatogonia. Figure 239 is the equatorial plate of a secondary
spermatogonium. There are 23 chromosomes, two of which are conspicuously
larger than the others and evidently form a pair. The odd one is one of
the three next in size.

Next to the secondary spermatogonia are cysts of young spermatocytes,
whose nuclei show a continuous spireme and an elongated deeply staining
chromatin rod which is the odd chromosome (fig. 240). This is often more
elongated than in the figure and more or less wormlike in appearance. A
pair of smaller chromatin masses may sometimes be detected at this
stage, and are readily found a little later (fig. 241) when the nucleus
has enlarged and the spireme has become looser and stains less deeply.
Here the odd chromosome is more condensed, or shortened, and split.
There is no synizesis and no polarized or bouquet stage, but the nuclei
of all of the spermatocytes contain a continuous spireme throughout the
growth stage. Synapsis must occur at the close of the last
spermatogonial mitosis before the spireme is formed. Figures 242 and 243
show a slightly later growth stage. The form and connection of the
"_m_-chromosome" pair (Wilson, '05_{b}) comes out clearly here. Figure
244, from a safranin-gentian preparation, shows both the odd chromosome
and the _m_-chromosomes. Some time before the first mitosis, the spireme
splits and the pairs of granules embedded in linin are wonderfully
distinct, both in iron-haematoxylin and safranin-gentian preparations
(fig. 245). The _m_-chromosomes have here formed a precocious tetrad
(_m_). Figure 246 is a similar stage from a safranin-gentian
preparation. Figures 247 and 248 show the condensation of chromatin
granules to form tetrads of various sizes, still embedded in the linin
spireme. As these tetrads come into the spindle without losing their
elongated form, it is evident that each one consists of two
longitudinally split c