Helen Dean King 347 
mann’s gentian-violet and safranin also proved of value as they differ- 
entiate the chromatin very clearly; they cannot, however, be employed 
to advantage in a study of the cytoplasmic structures of the cell. Ma- 
terial fixed in corrosive-acetic (5 per cent acetic acid) was stained in 
all cases with Delafield’s haematoxylin followed by orange G. 
THE PRIMARY SPERMATOGONIA. 
Testes of very young toads or those of adults killed in May and June 
contain many of the large, faintly staining cells to which La Valette St. 
George gave the name spermatogonia. In the testis of the adult these 
cells le, almost invariably, close against the follicle membrane; they 
are rounded in outline and contain a very large polymorphic nucleus 
(Fig. 1). A nucleus of this type seems to be characteristic of the 
primary spermatogonia of amphibians, as it has been found in these 
cells by most of the workers on amphibian spermatogenesis. A number 
of small cells, similar in appearance to the cells of the follicle membrane, 
are always to be found flattened against the primary spermatogonia 
(Fig. 1, F. C.). La Valette St. George (52) was the first to describe 
such cells in the testes of amphibians; and more recently they have been 
found by Meves (36) in Salamandra, by Janssens (23) in Triton, and 
by Kingsbury (29) in Desmognathus. It seems very probable that the 
cells surrounding the primary spermatogonia have the same origin as 
those on the follicle membrane, and that they are concerned in some 
way with the formation of the cyst walls which appear as soon as the 
primary spermatogonia have divided into daughter-cells. The follicle 
cells are much less noticeable after the secondary spermatogonia are 
formed; they are crowded in the spaces between adjacent cysts and no 
longer surround the separate spermatogonia. 
The resting nucleus of a primary spermatogonium contains an irregu- 
lar linin meshwork on which are distributed minute, faintly staining 
eranules of chromatin. A number of rounded nucleoli of various sizes 
are also scattered throughout the nucleus, being held, apparently, in the 
meshes of the nuclear reticulum. When material is examined that has 
been fixed in Flemming’s solution and stained with any of the com- 
bination stains used, all of the nucleoli invariably take the chromatin 
stain. If, however, testes are fixed in corrosive-acetic and stained with 
Delafield’s hematoxylin and orange G, some few of the nucleoli will 
stain with the orange, thus showing that they are plasmosomes; the 
greater number of the nucleoli, however, take the hematoxylin and are, 
therefore, to be considered as chromatin-nucleoli. Janssens also has 
