398 The Study of Zoélogy in Germany. [ July, 
spermatozoa seems to be very much the same in all vertebrates ; 
that is to say, the primitive cells of the testicular follicles divide 
into smaller cells, and the nuclei of these make the heads, while. 
their protoplasm changes into the tails of the spermatozoa. We 
have spoken of these changes here because it is proposed that the 
next paper shall be on the development and earlystages of eggs, 
and there will be occasion to refer to the observations just 
quoted. ; 
It is well known that cells create certain products which ap- 
pear outside of the cells themselves; thus wherever there is a 
layer of cells having a free surface, as, for example, the outside of 
the body of invertebrates or the walls of tubes such as ducts of 
glands, the digestive canal, etc., they tend to form a structureless 
membrane, which stretching over them all acts as a common 
protective covering. The hard crust of insects is such a mem- 
brane or cuticula, and a corresponding one lines the trachee and 
the stomach, etc., of insects.and many other animals. Now the 
application of section-making to the study of cuticular growths 
reveals many interesting peculiarities ; as this study is only just 
entered upon, it is hoped that a reference to some of the results 
may prove valuable. 
M. Léon Dufour described curiously shaped teeth in the crop 
of certain crickets, especially well developed in the mole-crickets, 
very large also in the katydids. Herr Wilde, of Leipzig, has 
made a very thorough study of these teeth and their devel- 
opment ; he kindly showed the author many of his preparations, 
and explained his results. He made numerous beautiful sections 
se of the crops of several species, both 
young and adult. Figure 72 is taken 
~ from one of his sections of the crop 
AN of Gryllus cinereus, the European 
gl field cricket. There are six teeth 
Jf] of very irregular shape, with many 
œ protuberances, but presenting, nev- 
Y] ertheless, the general outline of @ 
/. triangle, with the apex towar 
the middle. On each side of the 
ee 
(Fra. 72.) dki wiv iene secto or points, at the base of which there 1s 
THE CROP OF GRYLLUS CINEREUS. 4 bundle of stiff chitinous bristles. 
Between every two of these gigantic teeth there is a small oe 
(r) which also has a hard cuticula. Further, the teeth are n° 
