STRUCTURE OF THE TESTIS. 
203 
receptaculum seminis. A description of the receptaculum and its dncts 
in Phthirius is given by Graber. 281 
2. — Male organs. 
The close analogy between the male and female genital systems in 
insects is shown by the correspondence of their divisions, and has been 
repeatedly pointed out. The analogy in the way in which the sexual 
products are developed, though attention has been called to it, has not 
been so often emphasized. The testes are elongated sacks or tubes 
whose upper ends terminate blindly and whose lower ends open into 
the efferent ducts. The spermatozoa begin their development in the 
caecal end, in which, accordingly, we find the earliest stages always 
represented, while the more advanced zoosperms all lie further down in 
the sack, just as we find the youngest stages of the eggs in the upper, 
the oldest in the lower part of the ovarian tubules. The simplicity 
and distinctness of the parts and straightness of the seminiferous tubes 
in the grasshoppers renders the testes of these insects the very best 
object to demonstrate the development of the spermatozoa, with which 
I am acquainted, as in a single preparation all the principal stages are 
often distinctly shown. 
Testis.™ 2 — The male glands are composed of tubes which, instead of 
ascending from below forwards as do the ovarian tubes, incline from 
below backwards. The whole set of tubes is inclosed in a common sack- 
like envelope (Fig. G, p. 191, testis of Anabrus), and from this the tubes 
must be isolated. I have found the most convenient way of doing this 
to carefully harden a whole male insect in alcohol, and then to cut the 
whole abdomen in two along the median line, after which if a little 
pains is taken the single seminiferous tubes, which will be easdy recog- 
nized lying over the stomach, can be isolated under alcohol with needles. 
The following account refers to locusts only. The general shape of 
one of the tubes is shown in Fig. 25. The upper end is rounded off, and 
from the tip downwards it widens very rapidly, the tube soon attaining 
its maximum diameter, which it then maintains through the rest of its 
upper half; the lower half gradually tapers down to a comparatively 
small tube. The whole, when isolated in the manner described, is 
more or less surrounded by connective tissue, as shown in the drawing, 
conn. The tube may be roughly divided into four segments as indicated 
by the numbered brackets of Fig. 25. The upper segment [I] is filled 
with aggregations of cells in various stages of transformation into sper- 
matozoa, but still distinctively cellular in their appearance. In the 
second segment [II] the cells are gathered into distinct bundles, each 
bundle being as shown in the figure in a different stage of development, 
those lowest down being most advanced ; in Fig. 25 each one of the dark 
masses represents one of the bundles, each of which is composed of a 
281 Graber: Z. Z., xxii (1872), pp. 161-162. 
282 This account of the testis is taken mainly from Caloptenus spretug. 
