ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 639 



the foot of Haliotis, there are two large nerve-cords which arise from 

 the lower surface of the ganglionic mass which contains the pedal 

 and the asymmetrical (Lacaze-Duthiers) ganglia. Extending to the 

 hinder edge of the foot, they there terminate without undergoing any 

 anastomosis ; the two trunks are connected by several commissures 

 and give off a number of nerves ; the former arise from the ventral 

 portion of the cords, some of the peripheral nerves arise from the 

 outer edge, some from the dorsal portion, and some from the inner 

 face of the dorsal portion. These results, just as much as those 

 gained from a study of sections of the nervous trunks, prove that there 

 are two nerves in each of the pedal nerve-trunks, as Lacaze-Duthiers 

 had indicated. 



To this note Prof, Lacaze-Duthiers* added the following remarks ; 

 he pointed out that he had employed methods altogether different to 

 those of Spengel; he had not been content with a few dissections 

 or sections; he had made researches based on comparative studies, 

 and on the relations, which have been clearly established, between, 

 on the one hand, the nerves and the trunks from which they 

 arise, and, on the other hand, between the nerves and the parts to 

 which they are distributed. All methods, howsoever excellent, ought 

 always to be controlled by comparisons, and by a posteriori confirma- 

 tions. Any method employed absolutely and by itself may lead to 

 error, for morphology only furnishes certain results when we base 

 ourselves on anatomical facts which are incontestably true, and on 

 relations, well established by a series of comparisons leading to a 

 knowledge of the connections of different parts. In regarding the 

 epipodium as a structure connected with the mantle, he had in mind 

 the fact that no nerve from the pedal ganglion of a Gastropod ever 

 passes into the mantle, and that a nerve from the asymmetrical centre 

 never passes into the foot ; as we have here to do with two kinds of 

 nerves, it follows that we have two sets of parts or organs. He looks 

 upon the results of Spengel as being erroneous because they have not 

 been controlled by morphology. 



Pedal Glands of Mollusea.f — J. Carriere thinks that the openings 

 in the feet of Gastropods or LamelKbranchs are the orifices of various 

 glands ; water does not seem to be taken into the blood directly, 

 either by their pores or by the kidney ; nor is a quantity of water 

 necessary for the erection of the foot, for the blood alone can bring 

 that about. The renal cleft is not used as the means for introducing 

 water into the blood, but rather as a passage by means of which the 

 fluid which passes into the pericardium from the blood can make its 

 way into the kidneys. There are no indications of a water-vascular 

 system in either Gastropods or Lamellibranchs. 



Li pursuing his investigations the author found great assistance 

 from the air-pump, the use of which he learnt at the Naples Station ; 

 the thickest and largest pieces of the feet, which would otherwise have 

 required several days' treatment, were rendered easy of section after a 

 few hours. 



* Tom. cit., p. 277. 



t Arch. f. Mikr. Anat., xxi. (1882) pp. 387-467 (3 pis.). 



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