BRITISH SPONGIAD^. 289 



and is decidedly distinct from any of the numerous spe- 

 cies of that division of the genus, and I have there- 

 fore thought it advisable to designate it parasitica, in 

 accordance with the British Museum label 51.7.25 — 225. 

 The sponge does not coat the whole of the Zoophyte from 

 near the base to the apex without intermission, but it 

 occurs in a series of distinct masses of irregular forms, 

 none of them exceeding about an inch in its greatest 

 diameter. The specimen has unfortunately been so much 

 washed as to have destroyed the whole of its membranous 

 structures, nor could I distinguish any satisfactory traces 

 of oscula. The skeleton is very diffuse and irregular, but 

 unmistakably that of an Isodiotya. The primary lines, 

 although sinuous and irregular in their course, are well 

 produced, and continuously multispiculous j the irregularity 

 of the disposition of the primary lines of the skeleton 

 induces a corresponding effect among the secondary ones ; 

 and the whole aspect of the tissues become exceedingly 

 confused in their appearance. Much of this confusion 

 may probably have been the result of the excessive wash- 

 ing to which the sponge appears to have been subjected, 

 for occasionally small portions of the structure present a 

 very much more regular appearance than the principal 

 portion does. The spicula are very characteristic of the 

 species, they are subfusiformi-acerate, and are compara- 

 tively long and slender in their proportions ; much more 

 so than is generally the case in Isodictya. Imbedded 

 in the sponge, and frequently covered irregularly with 

 spicula, there were a considerable number of the ovarian 

 vesicles of the Zoophyte of an oval form, and very closely 

 resembhng the ovaries in Diplodemia, but a microscopical 

 examination of them when mounted in Canada balsam 

 quickly dissipates the illusion, as the cup-shaped lid at the 

 distal extremity of the vesicle becomes apparent by the 

 fine circular line that marks its junction with the body of 

 the ovarian vesicle, the lines of growth of which are 

 appsH-ently in accordance with its long axis, while those of 

 the hd or cap of the vesicle are decidedly concentric, and 

 at right angles to its long axis. The greater portion of 



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