390 X. AXNANM)ALE : Notes on Frcsliivnter Sponges. [\'OL. I, 



skeleton extremeh' massive^ especially so (but irre,e;ularly 

 arranged) towards the external surface ; a large amount of 

 spongin present in the skeleton. vSkeleton spicules short, 

 stout, smooth, straight or nearly straight, abruptly rounded 

 at the ends, but often with a verj- slender and minute ter- 

 minal projection ; no flesh spicules ; gemmule spicules slender, 

 cyhndrical, amphistrongylous, nearly straight, uniformly 

 covered with minute blunt spines ; arranged in distinct la5^ers, 

 one of which lies horizontally on the external surface of the 

 gemmule group, while the other is situated, with the spicules 

 l5dng tangentially, immediately outside each gemmule. The 

 gemmules small, spherical, grouped together in groups of 

 various sizes ; the " cells " surrounding them large, poly- 

 gonal in cross section ^ in many layers ; the main aperture 

 of each gemmule provided with a long, trumpet-shaped, 

 curved tubule, which opens outwards; subsidiary apertures 

 sometimes present. The gemmules occupying the whole of 

 sponge except a thin external layer, in wdiich the interstices of 

 the skeleton are small. 



In external appearance this species closely resembles 5. fragilis, 

 lycidy, a form widely distributed in Europe and America, recorded 

 from Australia, and lately found by mj'self in the Aluseum tank in 

 Calcutta, in which it was growing (together with 5. alba, S. 

 carter i , Ephydatia ftuviatilis var. nieyeni, Trochospongilla phillottiana 

 and T. latouchiana) on a brick wall. Spongilla crassior is, however, 

 most nearly related to mj^ S. crassissima, but its skeleton spicules 

 are stouter. The four Indian representatives of the subgenus are all 

 very close to one another, and I have had much difficult}^ in 

 separating them. As three of them are common in Calcutta and 

 I have, therefore, been able to examine a considerable number 

 of specimen'-, I think the following key will be found useful in dis- 

 tinguish'ng them : — 



SuBGriiiNTus Spongilla (gemmui,es bound together in 



GROUPS, EACH OF WHICH IS ENCI^OSED IN A MASS 

 OF POIvYGONAE " CEI.I.S "). 



A. Gsnini'.de spicules apparently not arranged in two layers — 



a. Skeleton spicules amphioxous ; fibres of skeleton 



delicate — Spongilla decipiens, Weber. 



B. Gemmule spicules clearly arranged in an outer and an inner 



layer — 



b. Framework of skeleton not very stout ; skeleton 



spicules amphioxous ; sponge incrusting — Spongilla 

 jragilis , Leid}". 

 b . Fibres of skeleton moderate, forming a close, hard 

 reticulation ; sponge forming spherical or spindle- 

 shaped masses — Spongilla crassissima, mihi. 



