SPERMATOGENESIS OF EUSCHISTUS 733 
mixtures were the ones mainly studied. Two principal stains 
were employed, the iron haematoxylin of Heidenhain and the 
safranin-gentian violet method of Hermann—the latter unequaled 
for many purposes. For the mitochondria in particular a num- 
ber of slides were stained with Meves’ modification of Benda’s 
method, but no precise differentiation was reached, other bodies 
always staining at the same time as the mitochondria. My 
clearest and most satisfactory stains of the mitochondria were 
reached with the iron haematoxylin method, in which it is best 
to use rather thick sections and to destain only slightly. .- 
The greater number of the drawings were made from two parti- 
cular testes, nos. 265 and 282, the former because it showed the 
mitochondria most distinctly, the latter because it was the best 
for the study of the chromosomes and the spheres. There is so 
much variation in small details between cells of correspondent 
stages from different testes that it seemed best to describe the 
phenomena as they occur mainly in one individual. Further, of 
the six longitudinal follicles of the testis, the cells of only follicles 
4, 5 and 6 were studied, for these cells are of approximately the 
same size; the large spermatocytes of follicles 1 and 3 present 
certain peculiarities that it seemed best to leave to a later special 
study.? 
The final writing up of this paper had to be done under great 
stress of outside duties, so that in my discussion of theliterature 
I may have made some important omissions. 
THE AUTOSOMES 
A. Observations 
Under the term ‘autosomes’ are meant the chromosomes of the 
ordinary type, in distinction from the modified chromosomes or 
allosomes that differ from them in behavior; this terminology was 
introduced in an earlier paper of mine (’06). 
2 On the differences of the cells in the six follicles, see my paper, 1910a. 
JOURNAL OF MORPHOLOGY, VOL. 22, No. 3 
