No. 3.] DEVELOPMENT OF MARINE SPONGES. 227 
others not. The protection made no difference. The protected 
and unprotected sponges lived for two or three weeks (and no 
doubt would have lived much longer if I had not grown tired 
of the experiment), undergoing practically no change, and 
apparently exempt from attacks on the part of the little fish 
and crustacea which swarmed round the mangroves. 
In preserving the Tedania material I was not as fortunate as 
I was later in the case of Esperella. For the Tedania embryos 
(larvae and attached stages also) I used Perenyi’s fluid and also 
osmic acid. Neither is nearly so good as the Zacharias mix- 
ture already spoken of, though of course they give fairly good 
results. 
2. DEVELOPMENT OF THE SWIMMING LARVA. 
Formation of Gemmules.— The gemmules are not confined 
to any particular part of the body, but are distributed more or 
less uniformly through the mesoderm. The very young gem- 
mules are simply imbedded in the mesoderm, Pl. XX, Fig. 69 ¢., 
but the ripe gemmules, ~ ¢., Pl. XX, Fig. 71, are provided with 
a definite sheath, g. s#., and are immediately surrounded by 
good sized canals. The gemmule of Tedania is puzzling, and I 
cannot claim to have actually disclosed its true structure. Still, 
the facts I have discovered, when compared with the develop- 
ment of Esperella, make it very probable that the gemmule of 
Tedania has essentially the same structure as that of Esperella. 
The ripe or full-sized gemmule of Tedania is a large spheroidal 
mass, in which neither cell boundaries nor nuclei can be made 
out. It is densely and uniformly granular, the granules being 
fine yolk granules (like the yolk in the cells of the Esperella 
gemmule) which stain well with any stain I tried (haematoxylin, 
carmine, cochineal, and other aniline stains). Repeated at- 
tempts with many stains on the thinnest of sections have 
failed to reveal nuclei, but it is possible that the employment 
of a different killing fluid would lead to better results. Some 
idea of the puzzling appearance of the deeply staining, uni- 
formly granular gemmules may be gathered from Pl. XX, Figs. 
71 and 70, the latter showing only a small part of a gemmule 
with the neighboring tissues. Strange to say, in the Tedanias 
