ON INCORPORATION BY SPONGES OP POREIGN SPICULES. 149 



ing the variety placed by Couch in plate lxxx. below the " Spanish 

 Mackerel" (S. scriptus), but which he observes that he " supposes 

 it to be a different species," it seems to be another variety in 

 colour of the common form, in which the first dorsal fin is a 

 little more forward and the second spine is slightly higher, if such 

 is not an error in the figure. He also observes that this variety 

 " has no air-bladder;" and likewise expressed his belief (p. 82) 

 that none is present in S. colias, although such has been described 

 in Cuvier and Yalenciennes's ' Histoire JNTaturelle des Poissons,' 

 1831, viii. p. 47; but not believing in its existence, Couch appears 

 to have fallen into an error. 



On two Cases of Incorporation by Sponges of Spicules foreign 

 to them. By Stuart 0. Ridley, F.L.S., Assistant in the 

 Zoological Department, British Museum. 

 [Read June 17, 1880.] 

 Two cases of this phenomenon, to the common occurrence of which 

 Mr. Carter has already called attention*, have recently come to 

 my notice while working out some Sponges from the southern 

 hemisphere, and they seem to me to be of some interest. The 

 one is that of a specimen assigned to the genus Ciocalypta, Bower- 

 bank, in which the dermis would be almost naked (a very unusual 

 character) but for the occurrence in it of certain long acuate 

 spicules having a very slight elongated basal inflation or head. 

 They are found scattered through the membrane, singly or in 

 loose bundles. The superior ends of the main skeleton-fibres 

 themselves reach the dermal surface, and there spread out like 

 the branches of the date-palm ; but they do not extend across the 

 surface to the same amount as in Ciocalypta penicillus aud C. Leei, 

 Bowerbank ; for here they do not meet their fellows to form the 

 lattice-like surface meshwork which is so conspicuous a feature 

 of those species. It is therefore in the vacant spaces left be- 

 tween the freely-terminating ends of the skeleton-fibres that the 

 subcapitate acuate spicules above mentioned are found. They 

 measure from -426 to '468 millim. in average greatest length by 

 •Oil to "01267 in thickness ; they taper gradually to a fine point, 

 and the head, which is only plainly discernible under a high power 



* Ann. N. H. (4) xvi. pp. 11, 16, xviii. pp. 230, 232. Cf. also Id. op. cit (5) 

 ii. p. 358. 



