SEASONAL CYCLE IN PERCH SPERMARY 697 
The germ cells come to their maximum size about August 5 
(fig. 34, a, b,c). At this time the entire testis in its normal small 
size is filled with solid cords of germ cells (fig. 30, G.c.). About 
5 per cent of the entire number have reached the maximum size; 
approximately 15 per cent are-still very small and apparently 
have but recently migrated, while the remainder represent in- 
termediate sizes. 
The cytoplasm of the largest cells is reticular and is free from 
darkly staining inclusions. The nucleus is remarkably hyalin. 
The linin threads are attenuated and the chromatin is well dis- 
tributed. In most cases the plasmosome is a large spherical 
structure which takes an acid stain, but in some cases the larger 
structure is absent and its place is taken by two or three smaller 
spheres. Figure 34 represents three cells taken from the same 
lobule, c representing a young germ cell before growth; 6, an 
intermediate stage, and a, a cell at its maximum size. 
Immediately upon. reaching their maximum growth the cells 
are transformed into spermatogonia. The proportion of the 
largest cells never increases to more than 5 per cent and the trans- 
forming cells are few in number. This would indicate that the 
time occupied in the final stage of growth and in the trans- 
formation into spermatogonia is short. The smaller and the 
intermediate cells are growing meanwhile, and there is a contin- 
ual procession of growth and transformation until late in No- 
vember. During late September and October each lobule shows 
a profusion of young growing germ cells, of germ cells at their 
maximum size, of transforming germ cells, of spermatogonia 
and of all the succeeding stages of spermatogenesis, including 
the mature spermatozoa. 
‘ 3. Period of transformation into spermatogonia 
During the transformation into spermatogonia two features of 
the process are outstanding: 1) There is a definite reduction in 
size. 2) There is a change in the chemical composition of the 
cells as shown by its capacity to acquire a deeper stain. 
