48 Mr C. Collier on the Sea-Slug of India. 



serrated ring*, and surrounded by twenty pinnated tentacula (ten- 

 taculis racemosis,Linn), Connected with and opening intoit are 

 many small, transparent, oblongbodies, (oneof which, always dis- 

 tended with fluid, is larger than the others) which, in the opinion 

 of M. Cuvier t, are secretory organs. The alimentary canal %, 

 and its retaining membrane (mesentere membraneux, Cuv.), have 

 been already described in the Lemons d'Anatomie Comparee ; 

 but the term Cloaca §, which has been employed, is applicable, 

 not to the termination of the intestine, which is smaller than the 

 rest of the canal, but to the kind of sac, formed by the transverse 

 membrane, into which the bowel opens. 



The vascular system |1 is so intricate and peculiar, that it is 

 indeed difficvilt, even after patient labour, to form a clear and 

 connected view of its constitution. The following is the result 



" M. Cuvier decides, but hastily I t'.iink, that this apparatus serves only 

 as a point of attachment for the longitudinal muscles : — " I^es Holothuries 

 ont bien I'ouverture de la bouche entouree d'un anneau, forme de dix pieces 

 demi-osseuses, mais ellesservent seulement de point d'apui aux muscles lon- 

 eitudinaux du corps, et aux tentacules recouvertes par la peau interieure de 

 la bouche, et ne contenant aucune dent, elles ne servent point a. la mastica- 

 tion. "Vol. iii- p- 336. 



+ Les Holothuries ont tout autour de leur bouche des sacs oblongs et 

 aveugles, qui debouchent dans cette cavlte, et qui ne peuvent manguer d'y 

 verser quelque liqueur analogue a la salive. Vol. iii. p. 340. 



+ The alimentary canal is of the same caliber, exceedingly delicate in its 

 texture, about four times the length of the animal, and disposed in three lines 

 of unequal length ; that is, it descends, returns to the right, crosses, and again 

 descends to the anus. The tenuity (and consequently apparent unfitness for 

 their office) of the tunics of the intestine, is found in some testaceous mol- 

 lusca also, and in those more particularly (as Murex tulipa and saxatilis, and 

 Trochus niloticm) which inhabit coarse shells. In the last mentioned species 

 the parts can seldom, with all care, be displayed without injury, and yet 

 very rough matter (as coral, and shells comminuted and entire) has to pass 

 along them. Fluid is found within the intestine, between portions filled 

 with solid matter ; and this fluid, like that within the cysts, which are ap- 

 iiended to the mouth, appears to be, from taste and appearance, sea-water. 



8 I/anus s'ouvre dans le grand cloaque situe a I'arriere du corps, et qui 

 n'est separe de la cavi'e de I'abdomen, que par une valvule. Vol. iv. p. 143. 



11 M. Cuvier bears testimony to the difficulty of this branch of the sub- 

 ject : " Je suis contraint d'avouer que, malgre tons mes efforts, je n'ai pu 



"encore parvenir a me faire des idecs certaines, sur I'organization des Echino- 

 dermes, a Tegard du systeme vasculaire." Vol. iv. p. 414. T have not been 

 able, I confess, even with the subject before me, to follow this able anato- 

 mist's demonstration. 



