no BRITISH SPONGES: 



ceive four or five smaller orifices opening in the interior of many 

 of these larger ones, the rim of which is always of denser struc- 

 ture than the rest of the surface, simple, circular and smooth. 

 When broken longitudinally, the fibres of the sponge are ob- 

 served to have an upright direction connected by numerous cross 

 threads fonned by fasciculi of the spicula, which are very nume- 

 rous, short, curved, fusiform, and pointed at both ends. 



Nothing can be more various than the appearances which H. 

 panicea assumes in different localities and sites. On sea-weeds 

 and corallines it often forms a thin crust which, after being 

 dried, is of a snow-white colour, and may readily be mistaken 

 for Grantia nivea without an examination of its structure. In 

 its normal state the surface is smooth, even, ridged or lobed, 

 with the pores so fine as to be imperceptible when the sponge 

 is fresh, and just visible after it is dried, while the fecal orifices are 

 scattered, either level or very little raised : this is very common 

 on rocks near low-water mark, and often surrounds the stem 

 of Laminaria digitata, nor is it uncommon on some crabs (Hyas 

 and Inachus) which it often entirely envelopes.* Another va- 



* My friend Mr William Thompson of Belfast writes me that he never 

 saw a specimen of Inachus scorpio which was not invested with sponge. 

 This reminds me of a curious habit of some Caribaean crabs detailed by 

 the late Rev. Lansdown Guilding : " The crustaceologist does not seem 

 to have accounted for the spurious legs, as he unjustly calls them, in 

 many genera of crabs, which appear in the works of European authors. 

 I once imagined that they were solely connected with the oviposition of 

 those curious beings, and in Lithodes arctica and the Porcellance (which 

 so beautifully connect the short-tailed with the long-tailed decapod Crus- 

 tacea) from their weakness and position they perhaps serve no other 

 purpose. In the Dromice, however, and some other genera, they are 

 quite dorsal, and wonderfully adapted to the purpose to which they are 

 applied, that of holding their house upon their back, as the spurious pos- 

 terior legs of the Paguri cling to the deserted shells they have seized 

 for their retreat. I have lately captured several specimens of these dor- 

 Mpedous Dromice having on their back knnses of sponges excavated and 

 fitted to their shapes, imder which they lie concealed while their prey 

 approaches. In one species the house was inimitably cut, ha^ing loop- 



