from the, South Coast of Devon. 11 



and Fuci ; growing from two-thirds beloAV high-water mark 

 downwards. 



Ohs. I found this sponge hj accident when chipping off a 

 portion of the rock on which Grantia nivea was growing ; 

 otherwise I should have passed it over ; for, living in the 

 cavities and under the overgrowths mentioned, it is almost 

 impossible to see it until the rock is broken. Having once 

 found its haLitat, it was very easy to procure specimens after- 

 wards ; for it is very abundant. 



Although occupying the cavities of SaxicavcVy whose deci- 

 duous shells are frequently present in the midst of the sjwnge, 

 I could never find any indication on them of its having bored 

 into them after the manner of the Clionid^e. 



On breaking open the rock, the contrast between the opales- 

 cent aspect of the sponge-substance and the black pigment 

 that it secretes over the cavities which it occupies is very 

 striking. By transmitted light, under the microscope, this 

 pigment presents a dark brown colour, which to the unassisted 

 eye is black ; but the layer is never continued over the dermal 

 sarcode, although the minute grains of sand and bits of shell 

 agglutinated to it are thus more or less blackened. The der- 

 mal layer, therefore, is always white, and particularly so in 

 the dried state, from the number of stellates which it contains, 

 while the rest of the substance in drying shrinks up into a 

 gum-like consistence and colour. In spirit and water, how- 

 ever, this retains its original bulk and compactness ; but the 

 opalescent aspect becomes changed to opaque lead-colour. 



On account, perhaps, of its isolation and its existence in 

 small portions while it remains in situ in the rock, when frac- 

 tured, those portions which are not much injured live for 

 several days afterwards ; and thus, from their smallness, being 

 easily brought under a high power of the microscope, the 

 currents outward and inward of the oscules and pores respec- 

 tively are as easily seen. 



In the specimens which I have mounted in balsam, the 

 variety of spicules is so great, and their abnormal forms so 

 numerous, that it is not easy to find out those which are the 

 staple ones. This variety, which is greater in some tlian in 

 other specimens, I am inclined to think may be induced by the 

 distm'bing influence of the waves, from which the sponge seems 

 to shelter itself as much as possible by growing solely in the 

 excavations mentioned. Possibly, if it also grows in the deep 

 sea, the quiet there may enable it to acquire larger dimensions, 

 and to present a less variable development of the spicules. 



It is desirable to add that in Stelletta lactea there are no 

 cells like those of the " celluliferous layer " in the two sponges 

 previously described. 



