214 Dr. J. E. Gray on the 



the " sphcro-stellate with conical points," and f. 166, with 

 " cylindro-subfoliate rays.") 



It is doubtful if some of these stellate specimens are not 

 produced by some of the layers being placed upon one an- 

 other; but this must be left for further study, as also such 

 elongate spicules with diverging spines as B. S. t. i. f. 35, and 

 the " elongato-attenuated " spicule, t. iii. f. 72. 



Mr. Carter figures beautiful forms of this spicule as occur- 

 ring in Chondrilla australiensis, and calls them sphcero-stellate 

 and radio-stellate (Ann. & Mag. Nat. Hist. 1873, xii. t. i. f. 16). 



6. The spicular spherules differ from the isolated spicules 

 before described by being formed of a multitude of parallel 

 needle-like or clavate spicules diverging from a central point, 

 and forming a solid globular or oblong mass with an areolated 

 surface. 



These spherules sometimes form the greater part of the 

 sponge, and at other times are found in conjunction with quin- 

 queradiate or trifurcate spicules. (See B. S. t. xxiii. f. 326- 

 328, t. xxiv. f. 329-334, t. xxvii. f. 353, t. xxviii. f. 354 ; 

 P. Z. S. 1872, t. x. & xi., and 1873, t. i. f. 6 ; Schmidt, 

 Spongienf. t. iv. f. 4.) Dr. Bowerbank, who compares the 

 anatomy of sponges to the anatomy of man, calls this mass of 

 spicules an "ovarium "■ — as he does the spicules of the sponge, 

 of which he observes that " those of Farrea have a very close 

 approximation to the tubular form of the bones of the higher 

 animals." The spherules certainly do not contain any eggs, 

 and are not even allied to the spore-cases of Spongilla : the 

 tubes of the latter are produced by the absorption of the spicule 

 which the fibres originally enveloped. 



7. The birotulate spicules in their most perfect state of deve- 

 lopment consist of cylindrical axes with an expanded more or 

 less circular disk at each end. They are almost exclusively 

 found in the substance of the case which surrounds the spore, 

 or, as Bowerbank calls it, the " ovary " of freshwater sponges 

 (Spongilla). Bowerbank figures several (B. S. t. ix. f. 210- 

 227). Sometimes the disks are very small, and the axis very 

 long (f. 210, 211) ; and sometimes the axis is very short and 

 the disk very large (f. 213). Sometimes one of the disks is 

 partially and at others almost entirely wanting (f. 223, 224) ; 

 and at others there is only a single circular disk, with the axis 

 reduced to a small central prominence (B. S. f. 225, 227). In 

 the two latter cases they have other names, being called 

 "boletiform slender" and " umbonate scutulate." The axes 

 in several of these spicules are more or less spinulose. 



It is very easy to arrange the sponges which have only one 

 of these types of spicules in company with simple unbranched 



