340 MR. ALBANY HANCOCK ON 



from C. celata. Dr. Bowerbank, however, denies the existence 

 of a second kind, a fusiform, or "acerate" spiculum, in any of 

 the British species.* This distinguished naturalist believes the 

 fusiform spicula described by me to be adventitious — adhering 

 accidentally to the surface of the sponge. Such belief is per- 

 fectly untenable. The fusiform spicula are not attached to the 

 surface as assumed by the doctor, but are imbedded throughout 

 the substance of the sponge in vast numbers : they are certainly 

 numerically equal to the pin-like form, as is stated to be the case 

 in the original descriptions of C. corallinoides and C. canadensis. 

 There is no more reason for supposing the fusiform spicula to be 

 adventitious than there is for assuming the pin-like forms them- 

 selves to be so ; both kinds undoubtedly belong to the organism. 

 It may also be stated that numerous foreign species, examined 

 by me, have similar fusiform spicula associated with the pin-like 

 form, and in many instances there is likewise present the third 

 minute kind already mentioned, as occurring in several of the 

 British species. But even when only the pin-like spicula are 

 found they are usually sufficiently characteristic to distinguish 

 the species. When, however, this form is, as just stated, asso- 

 ciated with other kinds of spicula, there can rarely be any doubt 

 on the subject. 



All the three forms of spicula are found in all the membranes 

 of the sponge. In such species as C. Nbrthumbrica, C. coralli- 

 noides, and C. vastifica, the pin-like form is the least numer- 

 ous, being only sparingly distributed in the internal membranes, 

 though they are densely crowded in the papilla?, where they are 

 arranged longitudinally, in parallel order, with the heads mostly 

 in one direction, so that when the papilla? are flattened or re- 

 tracted, they assume a radiating disposition. The fusiform spi- 

 cula are in vast numbers in connection with the external and 

 internal membranes, and occur also in the papillae, where they 

 are frequently arranged transversely. The minute spicula are 

 found everywhere, but in greatest numbers in the external mem- 

 brane, particularly on the papilla? : they are sometimes crowded 

 together in vast multitudes. In the species which have only 



* "Monograph of the British Spongiadse." Vol. II, p. 216. 



