OCR Text |
Show 4 PBOF. E. A. MINCHIN ON THE [May 2, authors have been in agreement as to the names to be employed for the genera or as regards the grouping of the species, especia y in the more primitive and interesting section of the Calcarea Homocoela. The characters, for instance, by which Breitfuss defines t e genus Leucosolenia of Bowerbank (1864) are such as would exclude from it all, or nearly all, the species which I should refer to it, including, as I have shown elsewhere, even Bowerbank s type species of the genus, L. botryoides ; while Lendenfeld has always consistently declined to make any use at all of the oldest generic name amongst the Ascons. In short, with the exception, perhaps, of the malarial parasites, there is probably no other group in the animal kingdom in which the nomenclature is in so confused a state as in the Homoccela. The species which forms the subject of the present memoir illustrates well the statement just made. It is a veritable comedy of errors that I have to set forth. The name Leucosolenia contorta was given by Bowerbank in 1866 [1] to certain small sponges from the Channel Islands- Guernsey, and the Guliot Caves, Sark. It is not very clear, however, what Bowerbank considered the distinctive characters of his species, since his diagnosis would apply to almost any Ascon. He states that " the form of this sponge is so distinctly different from that of L. botryoides that . . . . it cannot well be mistaken for that species . . . . L. contorta always appears to consist of a mass of contorted inosculating fistuke." Further, that " the external surface of L. contorta is also sparingly furnished with recumbent acerate spiculae, mostly disposed in a longitudinal direction, and I have never observed like spiculae on the surface of L. botryoides." He was a little doubtful if his sponge were not really identical with Spongia complicata Montagu (1816), but came to the conclusion that Montagu's figure of complicata was " really a very characteristic figure of Spongia botryoides of Ellis and Solander," and that therefore the name complicata was to be rejected. Finally, Bowerbank remarks that contorta and coriacea might be mistaken for each other in the dried condition, but that " the total absence of defensive spiculae on the cloacal cavity of L. coriacea " (meaning apparently the gastral rays of the quadri-radiates) readily distinguishes it. If we put Bowerbank's description into more modern terms, it amounts to this-that L. contorta was characterised (1) by form and appearance (contorted inosculating tubes), (2) by the presence of triradiate, quadriradiate, and monaxon spicules. The term " equiangular " applied by him to the triradiate systems need not be taken into account, since he applies the same term to the sagittal spicules of botryoides. It is not necessary to point out that the characters given by Bowerbank are not sufficient to define a species of Ascon ; and when it is seen that botryoides always has monaxon spicules, as I have shown elsewhere, and that contorta may frequently lack them ; that the specimen of botryoides from which Bowerbank figured spicules (Brit. Spong. iii. pi. i'ii. figg. 3, 4) |