PRESIDENT S ADDRESS. 



217 



our interest greatly, for it appears to be a persistently embryonic 

 Mytiloid with a wholly internal ligament. 



It may be doubted if, in our superfluity of discussion upon animate 

 nature as to what may have happened in the past, we are not prone 

 to overlook that which may be happening to-day ; and, f (jr this reason, 

 much interest appears to me to attach to a paper by Professor Bi'ooks 

 of Baltimore in which, returning to the study of an azygos, siphonal 

 tentacle, which he described in Yoldia in 1874, he adduces reason for 

 believing' that it is an organ "of late specialization, not thoroughly 

 settled in position." 



Continuing his work on tlio Pholadid;^), Sigerfoos, in a preliminary 

 paper full of interest, lias shown ^ that the larva of Xylotrya fiinhriata 

 is possessed of a long tongue-shaped ' foot ' with a byssus organ, 

 and of free mantle -lobes ; and that burrowing is commenced by a 

 conjoint mechanical action of the former and specially developed 

 ' shell-teeth.' It is an interesting circumstance that during 

 8igerfoos' investigation Lloyd has advanced good reason for con- 

 cluding ^ that in Pholadidea penita atrophy of the ' foot ' takes place 

 after that organ, by a muscuhir eilort and the utilization of ' grit,' 

 has excavated the burrow ; and that in the case of the unfortunate 

 oyster, Schiemeuz has adduced facts which sliow * the opening of the 

 valves by starfish, and Letellier ^ their excavation by the boring-sponge, 

 to be due to the exercise of sheer force. 



Had these discoveries been made in the telcological days of our fore- 

 fathers, the need of protection against starfishes would probably have 

 been accounted a sufficient explanation of the overgrowth of the 

 molluscan shell by the mantle. 



As our thouglits are thus directed to the shell-sac and the ' shell- 

 gland,' it may be remarked that ^>chmidt claims " to have confirmed 

 the observation of Gegenbaur, in 1851, that the shell of Claim Ha lies 

 originally in a closed sac. He asserts that the same is true of Succinea; 

 and his investigation heightens our interest in a problematical organ of 

 the young Sepia, which Hoyle in 1889 likened'' to the 'shell-gland,' 

 but which appears to me more nearly comparable to the aboral bursa 

 of St'piella. 



Tlie interest of Hoyle's observation is furtlier increased by the 

 recent discovery by Eather * tliat inuuediately after its liberation from 

 the egg- capsule the young Sepid attaches itself by a sucker-like expan- 

 sion of its mantle. 



' W. K. Brooks and G. Drew, Johns Hopkins Univ. Circ, vol. xv, p. 85. 

 ^ C. P. ,Siu;erfoos, t.c, p. 87. 



^ F. E. Lloyd, Science (n.s.), vol. iv, p. 188. Cf. also Zool. Auz., Bd. xx, 

 p. 14. 



* P. Schiemenz, Mitth.-Deutsch. Seefischereiver., Bd. xii, No. 6. Trausl. in Jouru. 



Mar. Biol. Assoc, (n.s.), vol. iv, p. 266. 



* A. Letellier, Bull. Soc. Linn. Normand., ser. IV, vol. viii, p. 149. 

 « F. Schmidt, Zoolog. Jahrb. (Auat. Abtli.), Bd. viii, p. 318. 



' W. E. Iloyle, Proc. Roy. Phys. Soc. Ediiib.. vol. x, p. 68. 



* F. A. Bather, Journ. Malac, vol. iv, p. 313. 



