100 
Fig. 23. 
Fig. 
Fig. 
24. 
29. 
ig. 30 
ol, 3 
BULLETIN OF THE 
An enlarged view of the head region, at about the same stage as the pre- 
ceding. 
PLATE V. 
A portion of the surface of a living egg of Agelena nevia, after the division 
of the blastema into polygonal areas. Several of the yolk corpuscles 
have shifted from their original positions, and therefore no longer 
coincide with the areas. X 165. 
Polygonal areas of the blastema and underlying yolk globules more 
highly magnified; from a living egg. X 440. 
Primary blastodermic cells before they become regular in form and size ; 
from a living egg. X 163. 
A portion of the blastoderm on the third day (temperature 23° C) of de- 
velopment; from a living egg. X 163. 
A little more than one half of the section of an egg, containing only one 
nucleus, the first segmentation nucleus; showing blastema (0/’.), 
nucleus (n/.), and yolk corpuscles (yk.). X 110. 
First segmentation-nucleus with the surrounding protoplasm highly mag- 
nified, showing also a rapid diminution in the size of the yolk cor- 
puscles in its vicinity. > 380. 
PLATE VI. 
Enlarged view of a portion of Fig. 28, showing the blastema (d/’.) and 
underlying yolk corpuscles (yk.). 
2. Isolated peripheral yolk corpuscles, to which portions of the blastema 
are attached. 
Isolated yolk corpuscie with a vacuole, which in turn contains a rounded 
yolk globule. 
Section through the nuclei of an egg in the two-cell stage, showing the 
two groups of yolk columns (Deutoplasmasaulen). XX 110. 
One of the deep internal cells, surrounded by yolk. 
A nucleus containing a central vacuole; from an egg in the two-cell 
stage. 
A migrating cell that has just reached the periphery, abutting on the 
blastema (0/’.). 
Detached portion of the blastema viewed from within, showing depres- 
sions into which the yolk corpuscles fit. 
89. Section of an egg passing transversely through the primitive cumulus in 
40. 
41. 
42. 
the region of its greatest width. X 110. 
PLATE VIL 
Radial section of two blastodermic cells. 
Section passing sagittally through the primitive cumulus. X 110. 
A blastodermic cell in the process of division, with ‘‘ interzonal filaments.” 
~~ 
et 
