CHITONID&. 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 
asymmetrical 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 m the latter the motive power is placed 
greatly more posteriorly than im 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 été impossible de trouver 
la seconde issue des organes de la génération ;”’ 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 m 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 
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