338 WHITMAN AND EYCLESHYMER. Vion: Aaike 
EXPLANATION OF CUTS 7 TO 12. 
Cut 7.— Vertical section of the same egg as that from which the section 
shown in Cut 6 was taken. Its position (dotted line in Diagr. F) is much 
nearer the centre of the egg. The section shows that the cells apparently cut off 
in Cut 6 are continuous with the yolk, the oblique character of the fourth (IV) 
cleavage grooves, and the elongated nuclei of the central cells. 
Cur 8.— Horizontal section of an egg in the same stage, in the plane indicated 
by the line 8—8 shown in Cut 6. It shows the central grouping of the vacuoles, 
and the depth to which the grooves have at this time cleft the yolk. 
Cut g.— Vertical section of an egg in the stage shown in Fig. 8, Pl. X VIII. 
The central cells have been cut by both horizontal and vertical grooves. Nuclei 
are present in the yolk. 
Cur 10.— Vertical section of an egg in the stage of early blastula, showing 
the cleavage cavity and the extent to which the yolk is now segmented. 
Cur 11.— Horizontal section of an egg in the same stage, in the plane of the 
dotted line 11-11 in Cut Io. 
Cur 12.— Vertical section of an egg in a late blastula stage. The calotte has 
begun to extend marginally over the yolk, and the epidermal layer is beginning to 
| differentiate. 

