2 Mr. H. J. Carter on the Suhspherous Sponges. 



neral observations showing liow far I agree and liow far differ 

 from the remarks of my predecessors on this portion of the 

 Spongiadaj. 



Two of the species which I have figured and described are 

 new, viz. the Arabian ones; and the other two are common to 

 om* own shores, but hitherto very inadequately represented. 

 Each contrasts in most respects strongly with the other, and 

 all four brought together in this way seem to me well fitted 

 to convey a good idea of the principal as well as peculiar fea- 

 tures of the subspherous Spongiadge respectively. 



My object has not been to pres t a mere description which 

 might serve for a handbook, but oj give an elaborate account, 

 with illustrations, of four of the most characteristic species of 

 the division, to correct to a certain extent what appear to be 

 the errors of others, and thus to record, to the best of my abi- 

 lity, descriptions and observations which might be relied upon 

 for future classification. 



In these descriptions I shall as much as possible avoid the 

 word "tissue;" for such is only shadowed forth in the sarcode 

 of the sponge, and, however much apparent in its fresh state, 

 more or less subsides into a glue-like mass on drying, when 

 tissue in the higher developments for the most part puts forth 

 its most definite, prominent, peculiar, and persistent charac- 

 ters. The tissues and the structures of the sarcode, whatever 

 they may be, are, for the most part, as it were in emhryo] and 

 we have nothing to do with the naming of objects, in a scien- 

 tific point of view, mitil they are unmistakably defined. 

 Hence such terms as ovaria, membrane, oesophagus, pyloric 

 valve, &c., in respect to the sponge, had better for the present 

 be omitted, whatever their application hereafter may prove 

 worth when such parts in the sponge are undeniably iden- 

 tified. 



In the following descriptions, also, it must not be expected 

 that I have given the whole history of the British species, 

 their habitat, locale, &c. ; this must be sought for in the works 

 to which I have alluded, my desire being chiefly to contrast 

 four prominent species among the subspherous sponges, two 

 of which appear to have been undescribed, and the other two 

 unsatisfactorily illustrated. 



The measurements (of course approximative) are chiefly given 

 in the explanations of the plates, to avoid confusion in the 

 text, and units indicating so many ISOOths of an inch or frac- 

 tions of the same (unless otherwise mentioned) have been 

 employed, by which the relative proportion of the objects in 

 size may be seen at once, and the real size readily computed 

 if necessary ; while the illustrations of the sponges themselves. 



