DECAPOD A. 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 each 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 

 branchio-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 this viscus, but prevents a retrograde 

 motion hy closing. Examined internally, the heart exhibits numerous 

 fasciculi and muscular fibres, variously intercrossed and forming se- 

 veral sin ill chambers before the orifices of the arteries. These 

 chambers arc 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 valvular ones above mentioned included. Such, with 

 tin- exception of some modifications f, is the general system of the 

 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 Barou Cuvier in his general report on 

 tin- 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 Esquissc 

 Distribution Generate du Regne Animal, p. 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 " Families of the Animal Kingdom," I beg leave to produce 

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

 ivier In partU'iilar, 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 dursal trunk of Fishc.s and of the larvae of the Batrachians ; that one or two 

 urtcrii."<. which in tlir Cephalopoda have the form of hearts, replace the right ven- 

 1 he focus of the circulation, highly concentrated in the first of the Verte- 

 brata, thu* becomes gradually \ve.iker, so that finally there is no circulation whatever, 

 .lorsal vessel of Insects would then be the mere rudiment of the heart of the 

 Mollusc* and Crustacea." I will udd, that twenty-five years ago, in my Hist. Nat. 

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

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



f See general observations on the family of the Macroura. 



j These observations are extracted from the Lefons d' Anatomic Comport* of Baron 

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

 and M. Edwards, loc. cit. 



