BEACHIorODS. 277 



several genera, as the Arcada^ and Pecten, the brancliial ves- 

 sels, instead of being connected parallel to one another within 

 the thickness of a connnon membrane, continue unconnected 

 through their entire length, and they are thus formed of a 

 great number of extremely delicate filaments attached by 

 the base within a membranous pedicle, in which the bran- 

 chial veins pvirsue their way towards the auricle. In a 

 great many families and genera the branchiae of one side 

 have no communication with those of the opposite side ; 

 in some others, however, as in the genus Unio, the four 

 branchial laminae meet under the foot, and the whole of 

 their vessels empty themselves into a venous sinus of consi- 

 derable size."* 



The Brachiopods, you will remember, derive their name 

 from the fringed and curled arms which they can evolve 

 beyond the compass of their valves ; and some comparative 

 anatomists have supposed that, whatever other use they were 

 of, was combined that of aerating the blood. The opinion 

 of Cuvier was different ; and the beautiful dissections of 

 Mr. Owen have proved that the true branchial vessels are 

 ramified, in rich profusion, upon the inner surface of the 

 lobes of the mantle, which are consequently the chief, if not 

 the sole respiratory organ. " In this profuse distribution of 

 vessels over a plain membranous expansion, we perceive 

 the simplest construction of the water-breathing organ, or 

 hranchia ; and, while it proves the close affinity of the Bra- 

 membranous surfaces of the gill, which remain connected only by the ver- 

 tically disposed vessels that give rise to the scjita ; they serve for the 

 reception of the ova, which, coming from the ovary placed within the 

 foot, and not by any means formed in the gill itself, are, however, lodged 

 there ; and there receive their farther develo])cment, as in a uterus. This is 

 a remarkable instance of the connection between the sexual and respiratory 

 functions." — Comp. Anat.,\iy\. ii. p. 148, 149, trans. — See also, Adanson 

 Senegal, pref. Li v. 



* Deshayes in Cyclop. Anat. and Phys. i. p. 699. Mr. Garner's sketch 

 of the variations of the branchite in the Lamellibranchiatcs is very interest- 

 ing. — Charlesworth's Mag. N. Hist. iii. 169. 



In the genus Solcnomya, Lam. there is a singular anomaly in the struc- 

 ture of the branchiae. " Branchiae duo non quatuor, nr)n lamelliformes, sed 

 pectinatae vel potius pennam exacte referentcs, lamellis transversis perpen- 

 dicularibus, carina media corpori per totam longitudincm adnata?, versus 

 a])icem ope ligamcnti." — Puilipi'i, MoL Sicil. i.p. 16. 



M. Valenciennes has observed, that tlie Lucinidse and Corbis possess only 

 a single branchia on each side of tlie foot and viscera ; and, at the same 

 time, the labial palpi, or accessory branchire, are all four wanting, — Ann. 

 and Mug. N. Hist. xvi. 43. Forhes and Hanlev, Brit. Moll. ii. 42, — In 

 Plioladomya and Anatina, Professor Owen had previously demonstrated 

 that tlie two lamellae of the same side are so united, as to appear like a 

 single gill. — Lect. Inverteb. Aiiun. 283. 



