422 BASHFORD DEAN. 
The germinal area, as above noted, is readily to be determined 
by the unaided eye, even at a very short time after the egg is 
Z RADIATA 
VILLOUS LAYER. 
Fig. 4.—Egg membranes of Amia. x about 180. 
deposited ; its margins fade gradually into the yolk somewhat 
above the equatorial region of theegg. Its marked appearance 
is doubtless the reason of the oblong form which the egg early 
assumes. This shape, moreover, would seem to bear with it a 
specialised developmental character in that it does not, in the 
event of the egg’s displacement, permit the germinal region to 
rotate backward into its vertical position, as it so readily does 
in the case of the sturgeon and gar-pike. The writer has 
found, however, in the early stages of segmentation that the 
cleavage planes occur in the normal way when the position of 
the egg was reversed. In these instances there was a slight 
attempt at the rotation of the germ disc, but in no case was 
this complete as far as the present observations went. The 
power of rotation in the eggs of Amia, it might here be noted, 
becomes more perfect at the subsequent stages of development ; 
toward the close of gastrulation the egg’s outline becomes more 
