Miscellaneous. 319 



Heart transverse and dorsal, Arterial circulation analogous to 

 that presented by the other Mollusca. 



The external orifice of the apparatus of circulation, placed above 

 the generative apertures upon the right side before the branchial 

 vein, in the form of a button-hole, is only visible in dead and much- 

 softened animals. It disappears with the greatest facility amidst 

 the wrinkles produced by the contractions. It communicates with 

 a canal which opens into the vein coming from the branchia, in front 

 of the auricle. The internal opening of this canal into the vein is 

 oblique, and placed upon a falciform fold directed towards the heart, 

 which may evidently play the part of a valve. 



All injections, whatever be their nature, or the means by which 

 they are propelled, reach the heart by this orifice from the ex- 

 terior. 



The external orifices of the circulation have not been remarked 

 and well determined upon the integuments of any of the Mollusca, ex- 

 cept the Dentalia and Pleurobranchi. In these examples ruptures 

 cannot have been taken for orifices. I hope to be able to gene- 

 ralize this fact, not by considerations independent of observation, but 

 by anatomical data, which everything leads me to think accurate. 

 I should mention that Gegenbaur, Leuckart, and Langer have already 

 indicated relations between the circulatory apparatus and the exte- 

 rior, by the intermediation, however, of the corpus Bojani either 

 directly or through the pericardium in the Pteropoda and Acephala. 

 We have this fact now demonstrated also in the Gasteropoda. 



It is evident, if we come to the generalization of these facts, that 

 the ideas we have of the nutrition of animals, taking the higher 

 creatures as our type, must be modified for the Mollusca ; and the 

 circulation in this group will no doubt present itself in quite a new 

 light. 



Nervous System. 



Three ganglionic centres, as in the other Mollusca. The supra- 

 cesophageal and pedal ganglia very distinct, forming a collar. The 

 right postero lateral ganglion (the same designated by authors by 

 different names, such as pallio-splanchnic, genito-respirator, &c.) 

 very small, placed close to the collar on the right side. 



This last centre furnishes two very slender nerves, of which one 

 passes to the generative organs, the other to the branchia. 



From the pedal centre the nerves of the foot arise. The otolithes 

 are applied against it. 



From the supra-oesophageal centre arise the nerves of the tentacles, 

 of the supra-buccal velum, of the trunk, the eyes, and the dorsal 

 tegumentary lobe. The two latter are very voluminous. One of 

 them, that of the right side, gives off very distinct filaments to the 

 branchia. It appears, therefore, that the right postero-lateral gan- 

 glia, called respiratory ganglia by some authors, are not the only 

 ones that preside over the function of respiration. 



The great sympathetic nerve is well developed, arises by two ori- 

 gins from the supra-cesophageal ganglia, forms two ganglia under 

 the oesophagus, and is distributed over the digestive tube and the 



