No. 3.] DEVELOPMENT OF MARINE SPONGES. 293 
20", The egg-cell has always a large nucleus with a very large 
nucleolus. In the cytoplasm there are usually several deeply 
staining bodies, each surrounded by a clear space. One of 
these bodies in Fig. 20’ is quite large. The bodies stain as 
deeply as chromatin, and I suspect them to be the remnants 
of engulfed cells. The occurrence of such bodies in the 
cytoplasm coupled with the fact that the outlines of the egg- 
cell are often indistinct in spots, suggests that the ovum is 
feeding on the surrounding mesoderm cells. In a very few 
cases I have met an egg-cell in the peculiar situation illustrated 
by Pl. XV, Fig. 20/”.. A gemmule, g, of about full size, is only 
partially surrounded by its follicle. The bare portion is con- 
tinuous with a thickly packed mass of mesoderm cells, in which 
lies the egg-cell, 0. ov. Pl. XVI, Fig. 20”, is a more highly 
magnified view of the bare end of the gemmule. The gem- 
mule cells, ¢, fade away into the less densely packed mesoderm 
cells, in the midst of which is the ovum, o. ov., surrounded by 
a follicle, ov. f, which was not present in the egg shown in 
Fig. 20’. It seems pretty clear that the gemmule, g, after 
reaching its full size, burst or absorbed its follicle and became 
continuous with the surrounding mesoderm. Only these very 
small egg-cells are met with, but they serve to indicate that a 
sexual breeding season follows the gemmular season. 
In this connection I may speak of certain gemmule-like 
bodies, which I am unable to explain, but which resemble a 
stage in spermatogenesis more than anything I know of. (See 
Fiedler’s figures for Spongilla, 5, and those of Vosmaer for 
Leucosolenia, 33, Taf. xxix.) Two of these problematical bodies 
are shown in Pl. XV, Fig. 17, pv. g., and another in Pl. XV, 
Fig. 14. They are comparatively common. They consist of a 
follicle inside which are small spherical cells entirely free from 
one another. The substance of these cells, if cells they are, 
stains feebly and appears homogeneous, and to the outer sur- 
face of each clings a crescentic band of chromatin. These 
bodies are always of small size, like those shown in Figs. 14 
and 17. Their size and follicle suggest that they are derived 
from gemmules. At first I thought they were degenerating 
gemmules, but their uniform appearance scarcely admits of this 
