102 Histology and Embryology. By C. S. Minot. 
tions of nuclei, as, for example, in tracing the development of sper- 
matozoa. The changes can be very well followed in sections of the 
testicle of Epicrium glutinosum, one of the Coeciliadae or footless, 
worm-like amphibians. The testicle is divided up into numerous 
follicles, and the cells in each are all in one stage, while the various 
follicles present various degrees of development ; thus in a single 
section all the principal alterations may be observed. The cells 
are round at first, with a very large granular nucleus. They then 
divide, becoming smaller and more numerous. The next change is 
a slightly irregular elongation of cell and its nucleus, slight at first, 
hut gradually increasing. At this point in the metamorphosis the 
protoplasm is gathered at one end of the cell, and the long nucleus 
at the other, and it at once becomes evident that the nucleus is to 
make the head of the spermatozoon, the protoplasm the tail. At 
this stage the cells lay themselves in rows, the nuclear ends, or as 
we may now call them the heads of the young spermatozoa, all 
pointing the same way. Each cell continues to elongate until it 
grows into a fully developed spermatozoon, with a pointed front 
end, a long head which appears almost black when stained with 
haematoxiline, and a long, fine tail. The development of the sper- 
matozoa 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 early stages of eggs, and 
there will be occasion to refer to the observations just quoted. 
It is well known that cells create certain products which appear 
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, &c., 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 membrane or cuticula, 
and a corresponding one lines the tracheae and the stomach, &c., 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. Leon 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 development ; he 
kindly showed the author many of his preparations, and explained 
his results. He made numerous beautiful sections of the crops of 
several species, both young and adult. In one of his sections of the 
