1-18 PEOCEEDINGS OF THE MALA.COLOGICAL SOCIETY. 



gut (Ilrh'j-), was known long ago, yet several modern books dealing 

 with ^loUusca still regard it as peculiar to the Acephala, and one, 

 published within the last twelve years, still retains the old exploded 

 idea of Mec-kel and Garner that the cfccum is connected with the 

 pharynx (forcgut) and represents the radula sac of the odontophora, 

 the style representing some part of the odontophore. 



The belief that the crystalline style was peculiar to the Dimyarian 

 Lamellibranchs has been long ago shown to be erroneous, this 

 structure being now known to be present in several Monomyarian 

 genera, as for instance Anomia,^ Ostrea, and Pecten ; it is not 

 however in all cases provided with a special ca3cum, but lies freely 

 in the lumen of the intestine : this may account for its presence 

 having been overlooked for so long, in spite of its large size — for 

 example in a specimen of P. maximiis, whose shell had a maximum 

 width of 4f inches, there was present in the intestine a crystalline 

 style 3J inches long. 



For full details of the relation of this structure as found in the 

 Lamollibranchiata I would refer those interested to Barrois' - very 

 full and detailed account, which deals with the historical, anatomical, 

 and physiological sides of the question. 



AVith regard to the function of this style and the sagitta or " fleche 

 tricuspide " Barrois comes to the following conclusions : he regards 

 the latter as a protective coating to the stomach formed at the 

 expense of the epithelium lining that organ, while the former he 

 considers to be a product continuously secreted by the lining 

 epithelium of the caecum, and gradually moved forwards into the 

 stomach by the action of the cilia, where it is dissolved by the 

 secretion of the digestive glands, and acts as a lubricant, covering 

 any sharp particles and enabling them to traverse the intestine 

 without damaging it. He considers in great detail the recent views 

 of Hazay^ and Haseloff* that the style is a reserve supply of food 

 material, but finds himself unable to support them, basing his 

 arguments largely on physiological grounds ; but he also tried Haseloff's 

 starving experiments, using Cardiiim instead of Mytilus, and obtained 

 no results — probably because he did not starve them long enough. 

 He also contests the view of Milne-Edwards ^ and others that the 

 style and sagitta have any masticatory function. 



Kespecting this last conclusion I think that, although the sagitta 

 is in the nuiin protective, it further serves, as does also the enlarged end 

 of the crystalline style, which abuts against the former, as a triturating 

 organ. I am especially led to this conclusion by the presence of the 

 large Foraminifcra in the stomach of Pterocera, that certainly are 

 broken up before entering the narrow intestine, and also from the 



1 Garner, Trans. Zool. Soc. ii. 1841, p. 89. 



2 Barrois, Revue Biol. d. Nord., 1888-89, pp. 124, 161, 263; 1839-90, pp. 209, 

 299, 351. 



3 Ilazay, D. Mollusken-Fauna v. Budapest, ii. Biologischen Tliiel. pp. 159-165. 

 Cassel, 1881. 



^ IlasL'L.lT. AV. d Krystullsiic] d. Muscheln. Osterode, 18S8. 

 ^ Mjluo- Edwards, Lc(,'(ius .s. I. ]'li\>i(ii. t. v. p. 302. 1809. 



