666 General Notes. (July, 
the same way in fishes as in Myriopods, viz., as a direct canalicu- 
lar vacuolization of the yolk passing through its central longitu- 
dinal diameter, the periblast would doubtless then represent the 
hypoblast or what it did in very primitive fish-like forms, while 
externally it would have been covered by a true splanchnopleure 
which had been developed in advance of the permanent hypoblast 
of the mesenteron, though the latter had been primarily derived 
from the primitive hypoblast. 
he eggs of the Myriapoda, it is to be remembered, represent a 
very peculiar type, that is, they at first have the germinal matter 
concentrated in the center, but as development proceeds the 
germinal matter, after segmentation into a number of cells, is 
repelled centrifugally or to the outer surface of the ovum. The 
primary segmentation therefore occurs in the center of the egg 
and not at one side or superficially until some progress in seg- 
mentation has been made at the center of the egg. This prob- 
ably characteristic mode of development seems to distinguish, in 
a measure, the Myriapoda from other Arthropoda, since in no 
other arthropodous form does the vitellus so constantly occupy 
a superficial position and so completely invest the first segmenta- 
tion cells, which are then aggregated in a cluster at the center of 
D 
place of publication of which is here cited, William A. Locy has . 
very carefully worked out the development of the spider (Age- 
lena), and obtained a number of new and important morpho 
results. He finds that there is at first a peripheral layer, 
protoplasm present, and that the nucleus of the first segmentation 
is central and imbedded in plasma. This first nucleus subdivides 
~ and gives rise to new nuclei, each invested by plasma. , ri 
ae migrate to the periphery of the egg and appropriate the peripher 
oe layer of protoplasm or “ blastema.” In this way a hollow blasto- 
peared not improbable that this depression repre ts the 
s egg W becomes 
invaginated. Later, and about 80° from the primitive cumit 
a second thickening. appears in the blastoderm ; this second thick- 
_ Between the. 
icker, thus lead- 
somites develop from the caudal plate, and wai : The mbry? 
‘the third as 1* 
