73 



outer surface of the fibre in all degrees short of absolute separation. 

 When viewed as transparent objects with a power of 300 linear, these 

 gemmular bodies appear to have a large opaque nucleus, of a some- 

 what granulated character, which fills the whole of its interior, and is 

 surrounded by a thin horny-looking shell or coat. The spicula are 

 exceedingly variable in size and form ; the greater portion of them 

 are slightly curved and attenuated towards each end, terminating in 

 some acutely and in others somewhat obtusely, (PI. vii. fig. 1) ; others 

 have their bases elliptical or globular, as in figures 2 and 3 ; occasion- 

 ally, though much more rarely, we observe them furnished with nu- 

 merous spines or tubercles, as represented by fig. 4 ; and still more 

 rarely they are multiradiate and of great comparative size, as repre- 

 sented at fig. 5. Two other spicula of an exceedingly curious form 

 were also observed ; the shaft of the spiculum being curved and the 

 terminations recurved, to such an extent as to form a large hook at 

 each extremity, as represented at fig. 6. I could not detect any pe- 

 culiar form of spiculum in the fleshy substance which fills the inter- 

 stices of the skeleton ; but I observed imbedded in its substance one 

 or two detached spicula of the form represented by fig. 1. This 

 fleshy matter is of a firm consistency, and has dispersed throughout its 

 substance numerous round or oval bodies, varying from $ V& to the 

 , T g of an inch in diameter, containing usually one, but sometimes 

 two nuclei. These bodies are nearly uniform in their colour and ge- 

 neral aspect, and present every appearance of being the cytoblasts 

 whence the cellular substance of the animal is derived. 



The results arising from the peculiarities in the structure of the 

 sponges which I have just described, are calculated in some measure to 

 modify the present arrangement of the Spongiadae, as published by Dr. 

 Fleming in his ' History of British Animals.' The occurrence of triradi- 

 ate and multiradiate siliceous spicula in the species first described, and 

 these forms having also been found in the Australian keratose sponge 

 which 1 published in a short paper in the ' Annals and Magazine of 

 Natural History,' vol vii., will render these compound forms of spicula 

 of comparatively little value as generic characters applied to either the 

 siliceous or to the calcareous sponges ; but their occurrence may per- 

 haps hereafter form useful specific characters. The other two singu- 

 lar and striking forms, the stellate and the fusiform spicula represented 

 by figs. 2 & 7 (PI. vi.), are each characteristic of a particular part of the 

 animal ; the first belonging to the fleshy substance, while the second 

 is indicative of the epidermis and its inflexions through the numerous 

 canals. In another British species of sponge which I have recentlv 



