40 
nor does a segmentative cavity make its appearance until 
much later. 
From the stage shown in Figure 1, up to the stage shown 
in Figure 10, no traces of a segmentation nucleus could be 
made out in the living egg, but at the stage shown in Fig- 
ure 11, a large, circular, transparent body appears in the 
first micromere and another at the formative end of the com- 
pound mass formed by the fusion of the second micromere 
with the macromere. 
At the end of the second period of rest (Figure 13), these 
bodies are much larger, and their outlines are very clear. 
The commencement of the second period of activity is shown 
in Figure 14, which is six minutes after Figure 13. The 
two spherules swell up and become much more conspicuous 
than they were at the stage before, although they are still 
in contact over a considerable area. The wave-like motion, 
noticed at an earlier stage, is now repeated in each spher- 
ule, and runs over the surface from the point furthest from 
the polar glotlue towards the end where this is situated ; the 
wave continuing for about half a minute. At the time this 
motion commences a remarkable change takes place in the 
two transparent vesicles already mentioned. Each of these be- 
comes irregular and star-shaped, and long channels radiate 
from it into the substance of the yolk, as shown in Figure 
47. The central chamber then instantly disappears; the 
radiating channels are visible for a fraction of a second 
longer, and then disappear, and the places which the two 
large chambers had occupied are now (Figure 14), seen to be 
•occupied by two small refractive nuclei. I at first thought 
that the radiating channels might be the same as the star- 
shaped figures of recent embryologists, but it seems more 
probable that each of the large chambers of Figures 11, 12 
and 13, contains a nucleus which might be brought out by re- 
agents, and which is surrounded by a more fluid substance, 
the diffusion of which through the yolk precedes the forma- 
tion of the amphiaster and the division of the nucleus. It is 
possible that this diffusion is the cause of the peculiar star- 
like arrangement of the granules of the yolk around the nu- 
