Linncean Society. 457 



tion throughout, and differ only in their arrangement and degrees of 

 concentration. The amount of the latter does not correspond with 

 the complexity of organization of the mollusk, but rather the re- 

 verse. 



1 1 . The organization of the vascular system is equally uniform ; 

 its completeness or incompleteness is no mark of complexity or sim- 

 plicity of the rest of the organization. 



12. The cephalous Mollusca are characterized by the possession of 

 a peculiar organ, the dentigerous " tongue," whose mode of action 

 resembles that of a chain-saw. 



13. The locomotive apparatus, when fully developed, consists of 

 four parts, the propodium, mesopodium, metapodium and epipodium. 

 These parts are least modified in such mollusks as Atlanta or Pneu- 

 modermon ; most altered and disguised in such as Cleodora or Oc- 

 topus. 



14. The term "mantle" should be confined to the surface of the 

 abdomen or post-abdomen, and to the prolonged edges of that surface. 



15. It is of great importance to recollect that the " shells" are 

 probably not homologous organs in all the different forms of mollusks. 



The shells of Sepia, Spirula (?), Limax, Clausilia and Helix are 

 developed in the thickness of the mantle. 



The shells of Nautilus (?), Pectinibranchiata, &c., are developed 

 from the surface of the mantle by a quite distinct process. 



Certain curious differences appear to follow the externality or in- 

 ternality of the shell. 



An external shell in a mollusk with a haemal flexure, e. g. Atlanta, 

 has its columellar axis below the aperture. 



An external shell in a mollusk with a neural flexure, e. g. Nautilus, 

 has its columellar axis above the aperture. 



An internal shell in a mollusk with a neural flexure, has its colu- 

 mellar axis below the aperture, e. g. Spirula, Clausilia, Helix. 



In the course of the memoir the author incidentally introduces a 

 number of new, and, as he believes, important facts, with regard to 

 the nervous, circulatory and urinary systems ; and describes at 

 length the mechanism of the " tongue" and an organ similar to the 

 "crystalline style" of bivalves, found in the Strombidae. 



LINN^AN SOCIETY. 

 March 16, 1852. — Robert Brown, Esq., President, in the Chair. 



Read a " Notice of the habits of Myrmica domestica, Shuck., to- 

 gether with some account of a means of turning the industry of 

 this minute Ant to account in the preparation of Skeletons of small 

 animals." By George Daniell, Esq. 



Mr. Daniell states that his attention was first attracted to this 

 species of Ant some years ago by observing several individuals 

 engaged, in the window of a house in Edwards Street, Portman 

 Square, in dragging to the edge of the casement a large fly, which 

 they finally succeeded in conveying through an opening in the wall. 



