Segmentation of the Ovtt 
00) 
'dtff/from Edler? 
Have a small segmentation cavity in the centre between them. 
This cavity increases in size in subsequent stages, its roof being 
formed by the small cells further divided, and its floor by the 
large cells, also multiplied by division, though to a less extent 
than the small cells. All the developmental processes progress 
more rapidly at the animal pole. After the equatorial furrow, 
there follows two vertical or meridional furrows which begin 
at the animal pole and divide each of its four cells into two, 
making eight small cells. After a short period these furrows 
extend to the lower pole and divide each of the large cells into 
two (Fig. 3, 5). The so-called meridional c\G3.vdiges Siiter the 
first and second are not truly meridional cleavages since they 
do not pass through the pole of the ovum, but through the 
poles of the cells, (blastomeres) which they divide; see Rauber, 
Morph. Jahrb. viii, 287. 
A pause now ensues, after which the eight upper cells be- 
come divided by a furrow parallel to the equator and someivhat 
later a similar furrow divides the eight lower segments. Each 
of the small cells is now again divided by a vertical furrow, 
which later divides also the corresponding large cell. The 
segmentation cavity is, therefore, now bounded by 32 small 
and 32 large cells. After this the upper cells (ectoderm) gain 
more and more in number beyond the lower cells (entoderm). 
After the 64 segments are formed, two equatorial furrows 
appear in the upper pole before a fresh furrow arises in the 
lower, making 128 ectodermal cells against only 32 entodermal. 
