346 AIMEE s. VANNEMAN 
least within certain limits. The primordial germ cell is large, 
being almost twice the size of an ordinary erythrocyte, and in 
contrast to the surrounding tissue cells, it takes a lighter stain. 
It varies in shape according to its location, but is typically 
spherical. At times the shape is very suggestive of amoeboid 
movement. Especially is this true in certain early stages to be 
referred to later. The cell outline is always definite. This is 
one of the surest criteria for the identification of germ cells. The 
cytoplasm is very pale and seems to be concentrated more or less 
closely around the nucleus, while the space directly within the 
cell membrane is practically clear. The nucleus too, is large in 
comparison to the nuclei of neighboring cells, and almost without 
exception is spherical in form. It may be noted that very fre- 
quently the nucleus is eccentrically placed. It is usually coarsely 
granular in appearance and always contains one definite dark 
staining nucleolus, frequently two, and sometimes more in 
younger stages. As the material used for this work was not 
fixed or stained for mitochondria, these bodies were not observed. 
Indeed, there appeared to be little need of using such criteria for 
the detection of germ cells, since the latter are distinct beyond 
suspicion without the aid of details. This statement may pos- 
sibly have to be modified in regard to very early stages. The 
question will receive discussion later in the paper. Concerning 
other criteria used by the various investigators for distinguishing 
germ cells, there is little to be said. Of course, yolk substance 
is not present in this case. Neither is the 'attraction-sphere' of 
Swift apparent, although the proper fixation and staining might 
reveal such inclusions. 
GERM CELLS IN EARLY STAGES 
Specimen 256 is the earliest stage in which I have been able 
to detect germ cells. It represents a condition where the lateral 
plates, which are to be the beginnings of primary buds, are just 
becoming differentiated through a shifting of cells of the young 
ectodermic vesicle. The plates are merely in the process of 
forming. At this time the germ cells are extremely few in num- 
ber. Indeed, not more than two could be found. They are 
