174 
J. BRONTE GATENBY. 
and 35, that the germ nuclei gradually lose all staining 
power, except that of the chromatic nucleolus, the reticulum 
disappearing. In later stages, when the germ cells begin to 
stain more heavily, only the nucleolus can be made to take 
up chromatin dyes. 
With regard to the migration of the germ-cells from out- 
side the embryo inwards (PI. 11, figs. 21 and 22, no pole 
canal could be recognised. The germ cells seem to sink in 
passively, and never become amoeboid as in Calligrapha 
( 3 ). 
The (Term C ell Determinant . 
The origin of the germ cell determinant, even in those 
insects where the eggs are larger and technique easier, is 
still in doubt. I have examined several Hvmenopterous 
insects parasitic upon Aphids, and find that the determi- 
nants appear as a cloud of granules towards the posterior 
pole of the egg. 
In Trichogramma the determinant is densest and most 
darkly staining during the period in which it still lies in the 
ovarian tubule, but is just about ready to lay (PI. 11, fig. 9). 
Py the time the egg has been laid and the polar bodies are in 
process of formation the determinant loses a great deal of 
its affinity for stains, and begins to break into pieces (PL 1 J, 
fig. 26, P, P.) At the blastoderm stage the determinant has 
completely disappeared, and with the exception of the rarest 
cases nothing of it remains (PL 12, fig. 36, G.). Indeed at 
at this stage the cytoplasm of the germ-cells, instead of 
staining more heavily than that of the somatic syncytium, 
as one would expect, has lost a great deal of staining power, 
both in nucleus and cytoplasm. This soon becomes very 
accentuated (PI. 11, fig. 22). In the newly laid eggs in 
PL 11, figs. 10 and 20, the germ cell determinant has become 
rather shrunken and faintly staining*, though in the case of 
Pi. 11, fig. 11, the determinant has a good deal more affinity 
for stains. 
