448 DR. J. S. BOWERBANK ON THE SPONGILLIDiE, [NoV. 24, 



acerate spicula, which are irregularly dispersed on their surfaces. 

 The birotulate spicula of the ovaria, compared with those of S. flu- 

 viatilis, present the most decided differential characters. The rotulse, 

 instead of being deeply incised at their margins, are only slightly 

 crenulate ; and their shafts, although longer in proportion than those 

 of the British species, are scarcely half their diameter, and nearly all 

 of them are incipiently spinous. Thus, notwithstanding their general 

 similarity in form, these differences in structure at once establish the 

 distinct specific character of this sponge. 



Spongilla Meyeni, Carter. 



Sponge massive, sessile ; surface tuberculous, hispid. Oscula 

 scattered, mostly intertuberculous. Pores conspicuous. Dermal 

 membrane aspiculous, thin, and translucent. Skeleton-spicula ace- 

 rate, stout, incipiently spinous. Ovaria subglobular ; spicula biro- 

 tulate, disposed in lines radiating from the centre of the gemmule ; 

 rotulse flat, irregularly but deeply dentate, divisions frequently ex- 

 tending to near the axis ; shaft from once to twice the length of the 

 diameter of the rotulse, cylindrical, without spines or with from one 

 to three or four near its middle. 



Colour yellow. 



Hab. Freshwater tanks, Bombay (^Carter). 



Examined in the dried state. 



I have received four specimens of this species from Mr. Carter. 

 The surface of all of them is profusely furnished with large tubercu- 

 lous projections ; on two of them these masses are rounded evenly, 

 and terminate nearly hemispherically ; while in the other two they 

 are more attenuated, furrowed longitudinally, and are rather sharply 

 terminated. These varieties of form are evidently the effect of dif- 

 ferences in locality only, as in all their organic characters they are 

 in perfect accordance. 



There is a remarkable coincidence in the organic characters of this 

 species and our European S.fluviatilis. The indistinct mode of the 

 arrangement of the skeleton, the form of the spicula of which it is 

 composed, the form of the ovaria and of their spicula are as nearly 

 as possible the same ; and it is only when we examine not only the 

 forms but the proportions of these organs, that we perceive that there 

 are really sufficient organic differences to constitute them distinct 

 species. 



The variation in the spicula of the skeleton is not very great, those 

 of S. Meyeni being -^-y inch in length, while those of S.fluviatilis 

 are but -J^ inch long. In the characteristic spicula of the ovaries 

 it is that the greatest discrepancy exists. In S.fluviatilis they are 

 remarkably constant in their proportions, being -y^TX ^"^^^ ^^ length ; 

 and the rotulse are as near as possible equal in diameter to the length 

 of the spiculum : the rule is, that the shaft should be without spines ; 

 and the occurrence of a single spine near its centre is the exception, 

 and this occurs in about the proportion of one to twenty or thirty 

 smooth spines ; while, on the contrary, in S. Meyeni the rule is the 

 presence of from one to four or five spines on the shaft, and the ex- 



