418 
CHIYOMATSU ISHIKAWA. 
pair of maxillae and the first pair of maxillipedes are provided 
with two such. 
The second and the third pairs of maxillipedes (figs. 72, 73, 
mxp. 2, 3) show no marked change except in size. The telson 
becomes more definite in outline. It is somewhat notched on 
its inner angles. Inside these notches, on the posterior border 
of the telson, are seen five rudimentary setae. 
The nervous striations have increased very much. Those 
going to the cephalic lobes expand into the shape of a fan in 
the anterior third of the lobe. The ocular pigments have 
also considerably increased. The ocellus has grown larger. 
The yolk-segments are now seen to have a radial arrange- 
ment with their nuclei on the periphery. These segments fuse 
together in the centre. 
Within the intestinal canal (fig. 75, in.) are already seen the 
concretions of extraneous matter. 
A longitudinal section through this stage (fig. 76), shows 
that the epithelial cells have been considerably formed at the 
periphery of the yolk-mass near the anterior end of the future 
hind gut (in fig. 76, just below the heart, h.). Five bundles 
of flexor muscles ( f.m .) are also seen in the abdominal region. 
Each of these consists of an aggregation of spindle-shaped 
cells, with oval nuclei. No striations have yet made their 
appearance within the cells. 
The yolk- mass, which up to this time has been uniformly oval, 
now changes its form. A large space (figs. 77, 78) is formed 
in front of the cephalic lobes by the absorption of the yolk 
there. On each side of the embryo, about in the line with the 
second pair of maxillipedes, a constriction occurs. A similar 
constriction takes place on each side of the cephalic lobes. 
Thus the yolk-mass shows five lobes, one antero-median, two 
lateral, and two posterior. The lateral and the posterior lobes 
later differentiate into the liver. 
About two days later the embryo presents the following 
characters. 
The anterior-median lobe of the mesenteron, which is seen 
in the last figure as a single lobe, becomes elevated from the 
