CONCHIFERS. 709 



surround the stomach and intestine, and pour the "bile by more than 

 one opening into their cavity. In many Lamellibranchmta there is 

 found, either in a blind appendage at the undermost part of the 

 stomach, or in the intestine itself below the stomach, a transpa- 

 rent elongated organ (the crystal style) , on that extremity of which 

 that projects freely into the stomach, a small membranous cartilagi- 

 nous protuberance, divided into three or more irregular processes 

 or points, is seated 1 . The use of this apparatus is not yet rightly 

 understood. POLI thinks the elasticity of the organ may press the 

 points of the protuberance towards and into the openings of the 

 gall-ducts, and thus moderate the influx of bile when not required ; 

 but such a regulator is unexampled in the animal kingdom. That 

 the style may effect the recoil of the foot, has been suggested by 

 GARNER, without any accurate explanation of the mode in which 

 this is produced, whilst, at the same time, the free projection into 

 the stomach of the tricuspid protuberance remains unexplained. 

 We confess rather that we do not yet understand the organ, 

 because we can compare it with no other in the rest of the classes 

 of animals. 



The circulation of the blood has in this class always a central 

 organ, a heart with a single ventricle, sometimes two hearts remote 

 from each other; for instance, in the Brachiopoda and in Area 

 amongst the Lamellibranchiata'*. In this case, however, the two 

 learts fulfil the same office on each side of the body, and are both 

 arterial like the single heart in the rest of the acephalous molluscs : 

 blood, namely, flows from the gills to the heart, not from the 



1 POLI names this protuberance sagitta tricuspis; see on this subject his celebrated 

 work Testae, utr. Sicil. I. Introd. p. 41, and the figures for example, from Pholas 

 dactylus, Tab. VII. figs. 9, 10, IT, from Tellina planata, Tab. XIV. figs. 9, 10, from 

 Cardium rusticum, Tab. XVI. figs. 13, &c. The circumstance that the crystal style is 



ometimes not to be found, and, as V. SIEBOLD thinks, is developed and disappears 

 )eriodically (Lehrb. d. vergl. Anat. I. s. 263, note 15), indicates an analogy with the 

 apides cancrorum (see above, p. 616) that promises, perhaps, to throw a clearer light 

 upon it. 



2 For the Brackiopoda compare CUVIER Memoire sur V Animal de la Lingula, 

 M6moires sur les Moll., and OWEN, Lettre a M. MILNE EDWARDS, Ann. d. Sc. Nat., 

 3ieme Se'rie, Zool. in. 1845, PP- 3 J 5 3 2O > a l so HUXLEY Contributions to the Anatomy 



the Brachiopoda, in Proceedings of the Roy. Soc. Vol. vii. pp. 106 117, 1854, who 

 ihrows some doubts upon the office of the so-called hearts ; their number, also, he 

 tates to be in some cases four. For Area see POLI Test. utr. Sic. n. pp. 182, 183, 

 ?ab. xxv. fig. i. 



