OSTREA. 43 



aeration from the atmosphere. The green colour, so 

 much prized by the Parisians, is owing to the oyster 

 feeding on the Navicula, a kind of Diatom or vegetable 

 organism which abounds in comparatively still and 

 brackish waters. According to physiologists the in- 

 testine passes the heart without coming into contact 

 with it, being an exception to the general rule with 

 respect to the relative position of these organs in the 

 Acephala. The oyster, therefore, cannot in fairness be 

 twitted with the proverb that the way to the heart is 

 through the stomach. Nor is the idea of its being 

 "crossed in love" less fallacious, seeing that each in- 

 dividual is of both sexes and can only be enamoured of 

 itself. Clark, as well as Gr. B. Sower by, asserts that the 

 animal has two adductor muscles, and that the corre- 

 sponding impressions may be seen in each valve, the 

 posterior one being very small and placed close to the 

 hinge. I have not been able, however, to detect more 

 than one impression, which lies nearly in the middle. 

 I would therefore invite the attention of naturalists to 

 the elucidation of this simple point. On it depends the 

 Lamarckian division of the Lamellibranchiata into 

 Monomyaria and Dimyaria, the oyster being the type of 

 the former group. Dr. Fischer says that the adductor 

 muscle in Pecten (which is allied to the oyster and 

 belongs to the same group) is divided, so as to form an- 

 terior and posterior bundles placed at different angles- 

 He is of opinion that the group of Monomyaria exists 

 only in appearance and not in reality. The cartilage 

 and ligament advance with the growth of the animal, in 

 consequence of which the old layers become useless and 

 are external. The oldest or first-formed portions of the 

 shell cease in time to be occupied by the animal, so that 

 the beaks become disunited and in adult specimens are 



