CHITONIDJE. 241 



symmetrical in their testaceous cones, are exceptions with 

 regard to the heart, auricle, and branchial plume : Haliotis, 

 which with me is a patelloid animal, and also an exception, is 

 the reverse, having the organs of the respiratory circulation 

 symmetrical, but not the cone. These, and two or three 

 other genera, may be regarded as the precursors of the Gaste- 

 ropoda, and as points of transition from the strict parities of 

 the cone of the shell and organs of the Patelloida, to the 

 asymmeti-ical division of the Gasteropoda. 



The only differences, and they are not important, with 

 respect to the position of the circulation in the Bivalves and 

 Chitons are, that in the latter the motive power is placed 

 greatly more posteriorly than in the former ; and the illus- 

 trious Cuvier has taught us to observe, that the auricles of the 

 Chitons have a quadruple connection with the heart, of which 

 he has seen no other example in the animal kingdom : this is 

 not stated in an objective sense, but as a curious fact, though 

 he gives no reason for this aberration of the usual structure. 

 Enough has now been said to demonstrate the little value of 

 the much-insisted-on dorsal rectilinear position of the motive 

 power of the circulation in Chiton, in comparison with the 

 Annelida. 



As to the objection to the allocation of these animals with 

 the Mollusca on account of the symmetry of the reproductive 

 organs, we think they are of small importance, even if double : 

 and who can say that the symmetrical Patelloida have not in 

 this respect a similar structure ? but these points are doubtful. 

 M. Deshayes says, " Quoique nous ayons fait des anatomies 

 minutieuses d'Oscabrions, il nous a ete impossible de trouver 

 la seconde issue des organes de la generation ;" and M. Cuvier 

 observes, they became so attenuated that he confessed he could 

 not trace them. Our own researches lead to doubts of these 

 appendages being oviducts ; at the same time we admit, they 

 may prove to exercise those functions : they are situate in the 

 immediate vicinity of the heart and auricles, and may be 

 glands to secrete a liquor for those organs, or the fecundating 

 pouches of the peculiar hermaphroditism of this tribe; in 

 which latter case, the true issue for the ova will probably be 



R 



