EMBRYOLOGY OF STOMOTOCA APICATA 
337 
egg is cut into two equal parts. The egg, viewed from above, 
at first shows a nearly circular depression which very soon spreads 
laterally and begins to grow down. This first furrow is wide and 
leaves the blastomeres separated from each other as it progresses 
downward, as is seen by looking at the egg from the side (figs. 4 
and 5). This furrow remains open until the egg is almost sep- 
arated into two parts; the blastomeres being connected simply 
by a narrow protoplasmic film at the lower pole. Protoplasmic 
currents can frequently be seen in this connecting thread. Bunt- 
ing (1893) describes and figures in Hydractinia a protoplas- 
mic thread in the two-celled stage in which she also notes proto- 
plasmic movements. The connecting film in Stomotoca apicata 
is not as clear and definite in outline as she shows it in her figure of 
Hydractinia. The two cells gradually come into close proximity 
and in a short time the connection of protoplasm at the lower 
pole is broken and the complete two-celled stage is found (fig. 6). 
The second plane of division is also meridional and at right 
angles to the first. This cleavage takes place about fifteen min- 
utes after the first. These second segmentation furrows start 
at the center and move out toward the periphery. During their 
progress outward there are to be seen globular or oval spaces at 
their outer extremities. These spaces are large enough to cause 
openings that extend through the egg as shown in fig. 7. During 
this cleavage there is a shifting or rotation of the blastomeres 
from right to left. The second segmentation furrows usually 
start opposite each other at a point in the center of the first cleav- 
age furrow, and then are carried apart by rotation; or the rotation 
may have started before the second segmentation began, in that 
case the second cleavage planes are some distance apart as soon 
as they make their appearance. Fig. 7 shows an egg in the proc- 
ess of division in which rotation has taken place. During the 
progress of the second segmentation, the egg has frequently a 
flattened appearance as seen in the figure just mentioned. 
In this stage protoplasmic films or bridges, also, frequently 
exist for a time after the segmentation is practically complete. 
They are finalh' absorbed by the blastomeres which then round 
up and form the completed four-celled stage as shown in fig. 8. 
