Mr. n. J. Carter on the Suhspherous Sponges. 3 



although drawn after nature as much as the subject would 

 permit, are less for effect tlian for efficiency, the microscopist 

 often having, in his delineations, to aim at that whicli an 

 artist would not tolerate nor could supply. 



Tetliya arahica^ mihi. 



PI. I. figs. 1-8, and PI. II. figs. 19 & 20. 



Globular and free, or hemispherical and fixed. Surface 

 soft, hispid, reticulated, with the pores occupying the inter- 

 stices, and projecting spicules the lines of reticulation, all more 

 or less matted together by the dermal sarcode of the sponge. 

 Large vents in more or less plurality, monticular. Internal 

 structure radiated, rigid, compact, consisting of a corticular, a 

 body-, and a nucleated portion. Corticular portion loose, ill- 

 defined, consisting of tufts of spicules matted together by 

 dermal sarcode. Body formed of sponge-substance supported 

 on bundles of spicules overlapping each other and radiating 

 from the nucleus to the circumference ; the whole permeated 

 by the excretory system of canals, which, branching and ana- 

 stomosing throughout, finally terminate in the vents on the 

 surface of the sponge. Fleshy portion of sponge-substance 

 more or less charged with minute spherical bodies like gem- 

 mules. Nucleus globular, consisting of a more compact and 

 dense condition of the spicules and sponge-substance of the 

 body. Spicules of the surface all smooth and pointed, con- 

 sisting for the most part of groups of bifid, trifid extended, and 

 trifid recurved heads, supported on long delicate sliafts respec- 

 tively, mingled with the pointed ends of the stout spicules of 

 the body. Spicule of the body straight, smooth, fusifonu, 

 pointed at each end, or not unfrequently with one end more 

 or less abruptly terminated and round. Minute ^ thread-like, 

 contorted spicules, semicircular and sigmoid, together with 

 minute siliceous globules, abound throughout the sponge, but 

 more particularly in the corticular portion ; somewhat larger 

 ones, of a semielliptical form, with single, pointed, incurved 

 ends, and others of a like kind, whose shafts consist of three 

 curves (of which the central is the largest), Avith trifid ends, 

 webbed together like a waterfowl's foot, and bent iuAvards, are 

 not uncommon in this sponge. Gemmules(?) numerous, white, 

 spherical, in all sizes of development up to the matured or 

 largest, which consists of a spheroidal cell filled with glo- 

 bules (?) of refractive matter; gemmule white, when viewed 

 by direct light, but by transmitted light seen to be surrounded 

 by an equally spherical transparent portion, or cell, densely 

 charged with extremely minute, bacilliform s])icular bodies. 



1* 



