es 
328 WHITMAN AND EYCLESHVMER. [Vora 
EXPLANATION OF CUTS 1 TO 6.* 
% ‘ : ; 4 
Curt 1.— Vertical section of the mature ovarian egg, showing the calotte, the 
germinal vesicle, and a portion of the yolk. 
Cur 2.—Vertical section of an egg at the beginning of the second cleavage. 
The position of the section is shown by the dotted line in Diagr. A. It shows 
the thickness of the calotte, the depth of the first cleavage groove (I) and the 
vacuolar spaces. 
Cur 3.— Vertical section in the stage of the third cleavage, in the plane of the 
dotted line in Diagr. B. It shows the depth to which the first (I) and third 
(III) cleavage grooves have extended, having now cut through the calotte and 
become continuous with the vacuolar spaces, which have enlarged and increased 
in number. 
Cur 4.— Vertical section of an egg in the same stage, but with the third verti- 
cals (III) arranged as in Diagr. C. The section passes near the margin of the 
calotte (dotted line, Diagr. C). The cleavage grooves have barely cut through 
the calotte, and the vacuolar spaces are less numerous than at the centre of the 
egg. 
Curt 5.— Horizontal section of an egg in nearly the same stage. In this case 
one of the third set of grooves (a), instead of taking a radial direction like the 
others, occupies the position shown in Diagr. D. The section passes just below 
the calotte, and shows that the cell cut off by this grooveis still in continuity with 
the yolk. 
Curt 6.— Vertical section of an egg in the stage of the fourth cleavage, in the 
plane of the dotted line in Diagr. E. It will be observed that the circular 
groove passes somewhat obliquely, and apparently cuts off two cells at the right. 
An examination of another section of the same egg (Cut 7) shows, however, that 
centrally these cells are in direct continuity with the underlying yolk. 
* Roman numerals indicate the order of the cleavage grooves. 

