1908.] ASPIDOBRANCH GASTROPOD MOLLUSCS. 819 



himself subsequently corrected his errors about the nervous 

 system, it is not necessar}^ to dwell on what is now a matter of 

 history. Failing to recognize the extremely fine supra-intestinal 

 nerve in any of the Neritidaj he dissected, he wrote with charac- 

 teristic emphasis, " 11 n'y a pas de commissure viscerale croisee," 

 and classed the ISTeritacea as " Rhipidoglosses orthoneuroi'des." 

 Following de Lacaze-Duthiers, he identified the swollen origin 

 of the subintestinal nerve with its sheath of ganglion-cells as the 

 subintestinal ganglion, but, curiously enough, did not observe the 

 large ganglion on the visceral commissure, afterwards discovered 

 and called the subintestinal by Bela Haller (20) and Boutan (6). 

 But his description of the nervous system is much in advance of 

 anything that preceded it. He was the first to discover the 

 course of the subintestinal nerve and of the left pallio-branchial 

 nerve. He discovered and described correctly the labial com- 

 missure, characteristic of the moie primitive prosobranchs. This 

 commissure, as he says, is " tres facile a preparer-," and it is curious 

 that Bela Haller, who succeeded in the much more diflicult task 

 of tracing the supra-intestinal nerve, should have emphatically 

 denied the existence of this very obvious labial commissure. 

 There is a further point of difi:erence between these two paithors, 

 in which Bouvier appears to me to be correct. Bela- Haller 

 describes no less than fourteen transverse commissures behind the 

 anterior commissure of the pedal nerve cords, whereas Bouvier 

 found, as I find, nothing more than fine nerves passing from the 

 inner sides of the cords to the muscles of the foot. In Bouvier's 

 brief account of some of the more important anatomical features 

 of Nerita peloronta there is a curious misprint, which has created 

 some confusion among some subsequent authors. On p. 47 he 

 writes : " Au fond de la cavite branchiale, a clroite, se trouve 

 la branchie bipectinee, libre en avant, en arriere rattachee au 

 manteau a droite et a gauche par un expansion de la lame 

 mediane, de sorte que le fond de la cavite bi'anchiale est divise 

 en deux etages superposes. A gauche de la branchie se trouve 

 le rein ; il s'ouvre dans la cavite branchiale par un orih'ce en 

 boutonniere situe dans la paroi anterieure du nucleus." The 

 words italicised ought to be tra,nsposed : the ctenidium, of course, 

 is on the left side of the mantle-cavity, and the kidney is 

 to the right of the ctenidium. Bouvier further describes the 

 so-called cephalic penis " toujours assez reduit dans les Nerites," 

 and gives a figure of a remarkable development of this organ in 

 jSferitina cariosa. Though his description and figure are not very 

 clear on this point, Bouvier appeai-s to have determined the true 

 position of the osphradium in Nerita, but as he did not examine 

 the structure of this organ and did not recognize the ganglia con- 

 nected with it, his determination is rather of the nature of a 

 conjecture than of proof. 



The next contribution to the anatomy of Kerita is that of 

 Kemy Perrier (34), whose researches were confined to the 

 kidneys and associated organs in Kerita peloronta^ Kerithia 



