and Oviducal System in the Lamellihranchiate Mollusks. 4i4i7 



M. Lacaze-Duthiers has discovered and described* yet another 

 route than that of the organ of Bojanus, by which, in the Den- 

 talium and Plewobranchus, water from without can find its way 

 into the interior of vessels carrying blood, and carrying it in 

 these instances towards the heart, and not towards the gills. 



Gegenbaurf differs from these authors merely in postulating 

 the existence of orifices of exit as well as of entrance for the 

 water; and these he holds to correspond with the puncta scat- 

 tered over the foot-surface, and visible in great abundance occa- 

 sionally along and near its free edge. 



Von Rengarten J exactly reverses the functions thus supposed 

 to belong to the punctated foot-pores, and the passage through 

 the organ of Bojanus severally. 



In a paper read by us§ before the Royal Society, February 3, 

 1859, we spoke of the water-vascular system as having its outlet 

 in close approximation to the external orifice of the organ of 

 Bojanus ; and its inlet we suggested might be indicated by the 

 position of the parasites which are not rarely to be seen studding 

 the foot-surface and marking out the presence of its numerous 

 pores. Gegenbaur, we observe ||, considers that the great lia- 

 bility of the foot to injury from the entrance of foreign bodies 

 into these pores is an argument for regarding them as exhalant 

 rather than inhalant orifices. 



Further investigations, carried on by us subsequently to the 

 reading of that paper, showed us that our views as to the oviducal 

 system in the Lamellibranchiata were founded in error. An 

 exceedingly courteous notice of this mistake by M. Lacaze-Du- 

 thiers^ in the 'Proceedings of the Royal Society^ rendered an 

 earlier retractation of this part of our paper unnecessary. Our 

 views, on the other hand, as to the permeation of the bodies of 

 the Lamellibranchiata by a system of vessels distinct from those 

 in which the blood is contained remain much what they were. 



Before stating our views, and the arguments by which we 

 would support them, we would say that the "perivisceral cham- 

 ber" of the Brachiopoda, as described by Mr. Hancock** in a 

 paper in the ' Philosophical Transactions,^ which was published 

 subsequently to the reading of our paper already referred to, 

 holds much the same relation to the circulatory and reproductive 

 and other viscera, as the system which we have called ''aqui- 

 ferous " in the Lamellibranchiata. As Mr. Hancockft has 



* Ann. des Sciences Naturelles, torn. xi. 1859, p. 255 ; Ann. Nat. Hist, 

 ser. 3. vol. v. p. 225. 



f Grundziige der vergleichenden Anatomic, p. 352, 1859. 



X Diss. Inaug. Dorpat, 1853, cit. Von Hessling, loc. cit. p. 236. 



§ Ann. Nat. Hist., ser. 3. vol. iv. p. 65. || Loc. cit. p. 352. 



II Ann. Nat. Hist., ser. 3. vol. v. p. 225. 



** Philosophical Transactions for 1858. Read May 14, 1857. 



tt J^oc. cit. p. 844. 



