DBCA-PODA. 157 



branches, running backwards, becoming gradually smaller and ter- 

 minating at the anus. The blood which has nourished these various 

 organs, and thus become venous, collects from all quarters into two 

 large sinuses*, one on eacli side and above the feet, and formed of 

 venous sacs united in a longitudinal series, or like a chain. It is 

 thrown into an external vessel — efferent — of the branchiae, where it 

 is renewed and becomes arterial ; thence proceeds into an internal 

 vessel — afferent ; and finally seeks the heart through canals 

 — hranchio-cardiac — laid beneath the arch of the flanks. All the 

 canals of a side unite in one large trunk, and open into the 

 lateral and corresponding part of the heart by a single orifice, the 

 folds of which form a double valve that opens to allow the transit of 

 the blood from the branchiae to tliis viscus, but prevents a retrograde 

 motion by closing. Examined internally, the heart exhibits numerous 

 fasciculi and muscular fibres, variously intercrossed and forming se- 

 veral small chambers before the orifices of the arteries. These 

 chambers are so many small auricles, which communicate freely 

 with each other when it dilates, but appear to form a similar number 

 of little cells for each vessel when it contracts, their capacity being 

 proportioned to the quantity of blood in their peculiar vessels. These 

 vessels debouche in the interior of the heart by eight openings, the 

 two lateral valvvilar ones above mentioned included. Such, with 

 the exception of some modifications f , is the general system of tlie 

 circulation in the Decapoda. 



The superior face of the brainj is divided into four lobes, each of 



* These learned naturalists compare them to the two lateral hearts of the Cepha- 

 lopoda, and the analogy has been admitted by Baron Cuvier in his general report on 

 the transactions of the Acad. Roy. des. Sc, for 1827 ; but the idea had been com- 

 municated by me to M. Audouiu, and was a necessary consequence of my theory 

 of the circulation of the blood in the Crustacea, published in a note of my Esquisse 

 d'une Distribution Genemle du Rhjne Animal, yt. 5. As the writers alluded to have 

 taken no notice of what I have stated in this particular, both in the pamphlet quoted, 

 and in my work on the " F<imilies of the Animal Kingdom," I beg leave to produce 

 that note. " I submit the following opinion to the judgment of Zootomists, and of 

 M. Cuvier in particular, viz. that in those of the Vertebrata possessed of a circula- 

 tion, the organ called heart represents, in its functions, a left ventricle, the arterial 

 and dorsal trunk of Fishes and of the larvae of the Batrachians ; that one or two 

 arteries, which in the Cephalopoda have the form of hearts, replace the right ven- 

 tricle. The focus of the circulation, highly concentrated in the first of the Verte- 

 brata, thus becomes gradually weaker, so that finally there is no circulation whatever. 

 The dorsal vessel of Insects would then be the mere rudiment of the heart of the 

 Mollusca and Crustacea." I will add, that twenty-five years ago, in my Hist. Nat. 

 des Crust, et des Insectes, I rectified the error of Rcesel respecting the nervous cord of 

 the spinal marrow, which had been taken for a vessel. 



f See general observations on ihe family of the Macrouva. 



X These observations are extracted from the Lefons d'Aiiatomie Comparce of Baron 

 Cuvier. For other details and particular facts, see the Memoir of Messrs. Audouiu 

 and M. Edwards, loc. cit. 



