NG IZ) re waGG “OF AMITA AND TESSCLEAVAGE, 341 
Figs. 29 and 30 represent eggs of about the same stage 
as that shown in Fig. 28. In Fig. 29 a radial symmetry is 
noticeable in the arrangement of the smaller cells, while in 
Fig. 30 a bilateral grouping is evident. Fig. 31 represents a 
third egg in about the same stage, showing the position and 
extent of the furrows, which at this time have reached the 
vicinity of the lower pole. A somewhat later stage is shown 
Ineipien es 2 
Cut 10 represents a vertical section of an egg about ro hrs. 
after deposition. The calotte is now from four to six cells 
thick. Beneath the central portion is the segmentation cavity, 
which at this time has become greatly enlarged through the 
confluence of the vacuolar spaces. In some eggs (e.g., Figs. 
18, 19) at this stage the cavity is so much enlarged that it 
appears like that seen in Amphibian eggs. The floor of the 
cavity is made up of large yolk segments. A horizontal sec- 
tion (Cut 11) of the same stage taken in the plane of the 
dotted line of Cut 10 shows the number and depth of the 
grooves at this level; above this level, near the equator, 
the grooves are more numerous. 
Cut 12 represents a vertical section of an egg 35 to 4o hrs. 
after deposition (late blastula). The calotte, which has now. 
begun to extend over the yolk, consists of thickly crowded 
spherical cells which marginally pass abruptly into the large 
yolk segments, while in the central portion they gradually 
increase in size and lie loosely scattered. The outer layer of 
the calotte is distinctly differentiated in that the cells are elon- 
gated and more densely granular. The entire yolk is irregu- 
larly cleft, the cells forming the lower portion are roughly 
polygonal and grade off into the large yolk spheres which lie 
at the centre. 
THE RELATION OF THE EMBRYO TO THE FIRST Two 
CLEAVAGE PLANES. 
The elongated form of the egg of Amia, in a closely applied 
envelope, prevents rotation about its minor axes. It is there- 
fore a favorable egg for ascertaining what effects, if any, gravity 
