31 8 LANGENBECK. [VoL. XIV. 
the outline of the cell distinct, but their protoplasm spreads 
out over the surface of the yolk, as seen in section (Fig. 47, 
ppl... As the cells in this region multiply, the protoplasm 
of one cell fuses with that of the surrounding cells (Fig. 
47, v.), so that it appears as though a layer of protoplasm, 
through which the nuclei are scattered, was spreading over the 
surface of the egg, as shown in Fig. 30. The large cell (Fig. 
30, @') near the region of the differentiated cells lies below 
the two small nuclei which are imbedded in the protoplasmic 
layer. The d! cell is almost always seen in this position, even 
before the ventral plate has reached that point (Fig. 34). In 
this case, therefore, it is unmistakably one of the dorsal cells 
which has been overgrown. 
As the embryo develops, the cells which are spreading dor- 
sally arrange themselves in definite rows corresponding to 
the rows of cells of the ventral plate. During the second 
day the yolk is completely overgrown by the ventral plate, the 
edges of which meet at the dorsal organ. At this stage the 
dorsal organ has moved to the center of the dorsal pole of 
the egg, and is composed of large triangular cells, whose apices 
are at the surface of the egg; the antennules are clearly de- 
fined, and the appendages could be seen just beginning to form. 
Fig. 31 represents an egg of the second day. The appendages 
have appeared asa series of ridges on the ventral surface, gradu- 
ally shading off dorsally, and it will be observed that the series 
extends over the posterior pole and dorsal surface of the egg, 
reaching almost to the dorsal organ (Fig. 36). The appendages 
are formed by the pinching off of from eight to ten parallel rows | 
of cells, and while being pinched off each ridge includes some 
of the cells of the lower layer from which the mesoderm of the 
appendage develops. This mode of origin of the limbs and 
their musculature recalls what has been figured by Dr. Bumpus 
(91) for Homarus. 
The embryo now elongates, the area of growth being chiefly 
in the dorsal region, posterior to the dorsal organ, as shown in 
Figs. 36-43. By comparing these figures it may be seen that 
the distance between the dorsal organ and the last appendage 
increases in extent, in consequence of which a fold appears on 
