34 WHITMAN. [Vou. II. 
in fifteen or twenty minutes after impregnation. They cause a 
flattening of one side of the yolk-ball, to see which it is often 
necessary to roll the egg over. The flat surface gradually be- 
comes a sulcus, giving a rentform outline to the yolk. It then 
extends all round, giving rise toa dumbbell shape. This sulcus, 
which may be termed equatorial, travels with considerable but 
variable rapidity towards the germinal pole, producing as it passes 
on, the flask form. The sulcus ts lost by passing forwards to the 
germinal pole, not by relaxation. It ts seen for a brief space 
affecting the thickness of the germinal disc only, to which it gives 
a nipple-like form, while the food-yolk 1s round. When effaced, 
the whole yolk-ball is globular and at rest, the germinal disc being 
no longer prominent. This sertes of forms recurs with more or 
less of vegularity, and with some variations both of time and 
form, about fifteen or twenty times, each series being the result 
of a travelling wave” (No. 14, pp. 463-464). 
Had Ransom succeeded in connecting the formation of polar 
globules with the more regular and prominent ‘wave,’ which he 
has so vividly described, he would doubtless have seen the neces- 
sity of distinguishing this wave from the movements which 
follow it, precisely as Kupffer and Benecke distinguished in 
the egg of Petromyzon a ‘zonal constriction’ which invariably 
accompanies the appearance of the second polar globule. They 
did not succeed in tracing the origin of the first polar globule; 
but they have described a constriction (p. 15) around the ger- 
minal pole (Fig. 7, 7), which appears immediately after the sper- 
matozoa come into contact with the egg; and this, I would 
suggest, may have the same relation to the first polar globule 
that the ‘zonal constriction’ has to the second. 
Polar Aggregation. — In the formation of the germinal disc 
of many pelagic fish ova, we meet with very remarkable cyto- 
plasmic movements. In the fresh-laid egg, the germinal proto- 
plasm forms a cortical layer of uniform thickness around the yolk. 
But this condition lasts only for a few seconds, during which the 
spermatozoon finds an entrance into the egg. This event is 
followed at once by a polar concentration of the peripheral layer 
of protoplasm, which results in the gradual formation of the 
germinal disc with its centrally placed pronuclei. 
Is it in one or both of the pronuclear bodies that we are to 
look for the cause of the polar aggregation of protoplasm? Is 
