348 WILSON. [Von. IX, 
of quite small spheres, but scattered about in the fine yolk are 
certain large rounded bodies which I take to be the first large 
spheres formed. 
While the egg is still small, long before it reaches the full 
size, the single nucleolus gives place to two nucleoli periphe- 
rally placed; as in Pl. XXIT1, Figs. 115.and 115%. » The egeof 
Pl. XXIV, Fig. 116, has likewise two nucleoli, situated in the 
same way, but the section passed through only one of them. 
Between the two nucleoli there is a sphere of granular mate- 
rial, which stains much less deeply than the nucleoli them- 
selves, and which is separated from the nuclear membrane by 
a clear space. When the egg attains its full size, one of the 
nucleoli is lost, leaving no perceptible trace behind. In the 
nucleus thus left with a single nucleolus, Fig. 117, the nuclear 
membrane could not be made out in my preparations, though 
the sphere of faintly staining granular material was obvious, 
Fig. 118 (portion of the periphery of such an egg as that of 
Fig. 117). The second nucleolus is then extruded, and may 
be seen lying in the yolk in the immediate neighborhood of 
the nucleus, which now consists exclusively of the sphere of 
granular material, separated from the yolk by a narrow clear 
space, Fig. 118. 
Segmentation results in the formation of a solid morula. 
An early stage in the segmentation is shown in the section, 
Fig. 120, and two morulas are shown in Figs. 121, 122. In the 
latter morula one of the segmentation spheres has been retarded 
in its division, and is consequently of a much larger size than 
the rest. Scattered between the segmentation spheres and 
forming a layer round them, there will be noticed a peculiar 
granular stuff which stains feebly but which is very conspicuous 
in the sections. It is probably a precipitate from the fluid bathing 
the segmentation, spheres, caused by the fixing fluid (Perenyi). 
V. REMARKS ON THE MORPHOLOGY OF SPONGES.! 
I have shown that in Esperella and Tedania the subdermal 
cavities, canals, and chambers develop as separate lacunae in 
1 The figures which illustrate this article, excepting Fig. 5, are borrowed. For 
their sources see description of the plates. 
