ANATOMY OF THE LAMELLIBRANCHIATA. 439 



Art. III. — On the Anatomy of the Lamellibranchiate Conchiferous 

 Animals. By Robert Garner, Esq., F.L.S. 



(Continued from Page 304.) 

 REPRODUCTIVE SYSTEM. 



Reproduction in these animals was supposed, by some of 

 the ancient naturalists, to take place by a spontaneous gene- 

 ration, without the existence of ova ; but this idea has now 

 been justly exploded. Some modern naturalists have main- 

 tained, that amongst bivalve species, some individuals are 

 male and others female. Leuwenhoek 1 inferred this, as did 

 also M.M. Prevost and Dumas; 2 and that the ova of the fe- 

 male, after their rejection, required to be fecundated by the 

 fluid of the male. Mery 3 supposes the existence of male and 

 female organs in every individual, but that an union of two 

 individuals is required for impregnation. But there appears 

 every reason to believe that there is no difference in the indi- 

 viduals, as to sex, and that the ova are discharged from the 

 ovaries in a state fit to develope, without the necessity of the 

 contact of any vivifying fluid ; or, in other words, that they 

 are fecundated before they leave the ovaries, by testes which 

 must be conjoined with those organs. No distinct male or- 

 gans appear to be present. Perhaps Home, 4 who mentions 

 their existence, has mistaken the excretory organs for them, 

 as have many other anatomists. From what the author has 

 observed in the Modioli and My Mi, he believes that the or- 

 gans called ovaria do, at certain periods, secrete the seminal 

 fluid, which impregnates the ova contained in them, and is 

 then discharged as an excretion by the oviducts. 



These ovaries are always voluminous, containing immense 

 numbers of ova. 5 They are not always circumscribed, but 

 their ramifications vegetate, as it were, into different parts of 

 the body. Though two oviducts are developed, the ovaria 

 are not always distinct from each other, and sometimes, as in 

 the Pecten, all the ova appear to be discharged by one ovi- 

 duct alone. When the foot is imperfectly developed, the ova 

 at certain periods are seen to distend the mantle, as in Myti- 

 Ins, Modiola, Lithodomus, Hiatella, &c. In the oyster they 

 are found externally on each side of the liver, and also form 



1 Arcana Naturae. 2 Annales des Sci. Nat. vol. vi. 



3 Mem. Acad. Sciences. 1701. 4 Lectures on Comp. Anatomy. 



5 Poli says the ovaries of a single oyster contain 1 ,200,000 ova. 



