CONCHIFERS. 709 
on 
surround the stomach and intestine, and pour the bile by more than 
one opening into their cavity. In many Lamellibranchiata 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!, The use of this apparatus is not yet rightly 
understood. Poxt 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 Arca 
amongst the Lamellibranchiata®. In this case, however, the two 
hearts 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: 
the blood, namely, flows from the gills to the heart, not from the 
1 Pott names this protuberance sagitta tricuspis; see on this subject his celebrated 
work Testac. utr. Sicil. 1. Introd. p. 41, and the figures for example, from Pholas 
dactylus, Tab. vu. figs. 9, 10, 11, from Tellina planata, Tab. xiv. figs. 9, 10, from 
Cardium rusticum, Tab. Xvi. figs. 13, &c. The circumstance that the crystal style is 
sometimes not to be found, and, as V. SreBoip thinks, is developed and disappears 
periodically (Lehrb. d. vergl. Anat. 1. s. 263, note 15), indicates an analogy with the 
lapides cancrorum (see above, p. 616) that promises, perhaps, to throw a clearer light 
upon it. 
2 For the Brachiopoda compare Cuvier Mémoire sur VAnimal de la Lingula, 
Mémoires sur les Moll., and Ownn, Lettre &@ M. Mitne Epwarps, Ann. d. Sc. Nat., 
3itme Série, Zool. 11. 1845, pp. 315—320, also Huxtry Contributions to the Anatomy 
of the Brachiopoda, in Proceedings of the Roy. Soc. Vol. vu. pp. 106—117, 1854, who 
throws some doubts upon the office of the so-called hearts ; their number, also, he 
states to be in some cases four. For Arca see Pout Test. utr. Sic. 1. pp. 182, 183, 
Tab, xxv. fig. 2. 
