474 
The American Naturalist, 
first ; the surface of the germinal disc is cut up into four seg- 
ments or quadrants, (Fig. 5, A.) which are not, however, sep- 
arated from the underlying substance. The number of radiat- 
ing furrows increases from four, to seven or nine, when there 
arises a series of irregular cross furrows, by which the central 
portion of each segment is cut off from the peripheral portion 
giving rise to the appearance illustrated by Fig. 5, C; there 
are now a number of small central segments surrounded by 
large, wedge-shaped external segments. Division of the seg- 
ments proceeds rapidly by means of furrows running in va- 
