564 General Notes. [June, 
size as compared with those of other types. Two polar globules 
arise side by side and not one beneath the other, as in other cases, 
_ As many as five distinct polar globules were extruded in abnor- 
mal cases, and the extremity of one of these was enlarged into a 
globular form, the same as one of the two in the case of the 
normally developing egg. The polar cells finally become much 
reduced in size and are easily detached from the egg. 
: The ‘segmentation is slightly meroblastic and a hollow blastula 
is soon formed; hatching occurs in about ten hours, when the 
apical cells and the two equatorial rings of velar cells have become 
ciliated. At the vegetative pole of the blastula four large, so-called 
endo-mesodermal cells, forming part of the wall of the blastula, are 
elongated and prolonged into the blastoccel and two of them have 
their inner ends segmented off to form the primitive mesoderm ; the 
other two and what remains of the two preceding ones give rise to 
the endoderm or intestine, while the decreasing area on the outside 
_ of the blastula embraced by the endo-mesodermal cells represents 
the blastopore. The primitive pair of mesoblastic cells are bilateral 
in position and render the larva bilaterally symmetrical. The 
blastoporic area gradually assumed a more ventral position 
and is then shoved forwards and inwards, finally disappearing 
at the bottom of a deep furrow which partially closes or concr s: 
i On either side of the posterior 
part of the stomodæal furrow there is a swelling ; this pair 
of the foot, on either 
lave segmented into a row of three cells each, lying symmetri- 
cally on either side of the median plane of the embryo. A glos- 
s, and the 
carried ventralwards and forwards leading to the formation of the 
of bilaterally 
0- 
