No. 3-] DEVELOPMENT OF MARIAE SPONGES. 327 



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 Gcmmttlcs. — 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, PI. XX, Fig. 69 _^., 

 but the ripe gemmules, r. g., PI. XX, Fig. 71, are provided with 

 a definite sheath, g. sli., 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 (haemato.xylin, 

 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 PI. 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 



