CONCHIFERS. 711 



plates described are gills, BOJANUS entirely recedes ; he thinks that 

 the only office of these organs is the custody of the eggs, whence 

 he does not name them gills, but brood-receptacles (Bruthalter) . 

 Accordingly he has described an entirely different organ, not 

 noticed previously, as a respiratory organ 1 . According to his ob- 

 servations the venous blood, that flows back from the organs of 

 the body, is conducted to an elongated venous sinus situated at 

 the dorsal surface beneath the heart. Close to this sinus are 

 two spongy, dark-green or brown sacs, which are very rich in ves- 

 sels, and receive all the blood from the venous sinus. BOJANUS 

 was of opinion that these organs serve for respiration, and are 

 lungs; from each sac arises a single vascular stem, which runs 

 along the two gills of its own side. From the parts which BOJANUS 

 names lungs, come also some short vessels, which run immediately 

 to the heart, but the greater part of the blood that flows in them 

 goes to the two vascular stems of the gill-plates. 



The investigations of BOJANUS have made us much more accu- 

 rately acquainted with the circulation of the blood in Lamelli- 

 branchiata, than what had previously been written upon it. The 

 mode, however, in which this anatomist explained what he observed, 

 is exposed to many objections. If his opinions be not adopted, it 

 is not clear what appellation ought to be assigned to the organs 

 described by BOJANUS. At the present day it seems that these so- 

 named lungs are very commonly regarded as kidneys 2 . On this 

 supposition, however, it remains unexplained why they receive 

 all the venous blood of the body. This circumstance deserves 

 special consideration, whenever a conclusion is attempted con- 

 cerning the nature of these organs. Hence it is that I offered, 

 now more than twenty years ago, the opinion that these so- 

 called lungs are venous sinuses, as much as the part that lies 

 between them, which BOJANUS himself named sinus venosus / they 



Animate, p. 283. Also in Lucina and Corbis VALANCIENNES found only a single gill 

 on each side ; Comptcs rend us, 9 Juin, 1845, 



1 L. H. BOJANUS Sendschreibcn a Mr le Chevalier G. DE CUVIER iiber die Athem- und 

 Kreislauficcr'kzmye der zweischaaligen Muscheln insbcsondere dcs Anodon cyyneum. 

 Mit abbildungen, 4to. (Printed separately from OKEN'S Isis in 1820, Heft 7). POLI 

 speaks in different parts of his work of this organ, under the name of viscus testaceum, 



2 TREVIRANUS Zeitschr. f. Physiol. i. 1824, s. 53 ; CARUS Lehrbuch dcrZoolomie, 2te 

 Aufl. n. 1834, s. 650; V. SIEBOLD Lckrb. d. veryl. Anat. I. s. 281 284. 



