94 A MONOGRAPH OF THE 



young naturalist, whom we have lost in the prime of his 

 intellectual development, for my first knowledge of the 

 mode of external development of the gemmules of this 

 species. He found them pullulating from near the base of 

 a specimen of the sponge which he obtained in the neigh- 

 bourhood of Plymouth; and subsequently, on the 26th of 

 January, 1862, I found six of the gemmules around the 

 base of a living specimen which was dredged at the Diamond 

 ground, off Hastings. The parent sponges and the gem- 

 mules in each case very closely resemble each other. Each 

 of the gemmules was attached to the parent sponge by a 

 fasciculus formed of several skeleton spicula; the bodies 

 of the gemmules were quite separated from the Tethea, 

 and each gemmule had its own distinct groups of radiating 

 spicula. I have never succeeded in finding internal gem- 

 mules in any specimen of the sponge in which I have 

 searched for them. 



5. Tethea spinularia, Boiverbank. 



Sponge. Massive. Surface even, minutely hispid. Oscula 

 terminal, slightly elevated. Pores inconspicuous. Der- 

 mis coriaceous, thick. Dermal membrane pellucid, 

 furnished at intervals with fasciculi of minute acerate 

 spicula ; spicula of the fasciculi very numerous, slightly 

 curved, disposed parallel to each other, with the curves 

 in accordance. Skeleton. Spicula subfusiformi-ovo- 

 spinulate, long, and rather stout. External defensive 

 spicula continuations of the skeleton fasciculi. Dermal 

 defensive spicula fusiformi-ovo-spinulate, short and 

 stout, disposed at right angles to surface, very nu- 

 merous. Tension spicula sub-fusiformi ovo-spinulate ; 

 as large as those of the skeleton, irregularly dispersed, 

 numerous ; and also fusiformi-acerate, fasciculated like 

 those of dermal membrane ; fasciculi few in number. 



Colour. Dried, gray, with a tint of green. 

 Habitat. Shetland, Rev. A. M. Norman. 



