224 SUMMARY OF CURRENT RESEARCHES RELATIKG TO 



with tlie pedal ganglia, careful research has never failed to show that 

 the auditory nerve can be followed to tlic cerebral ganglia ; in the same 

 way, whatever be the form of the mantle or the f<iot, whether they fuse 

 or not, it is always possible to discriminate between them by means of 

 the nerves which are distributed to them. " Sections only show what 

 they inclose, and the explanations of them, which are sometimes 

 based on deceptive phenomena, cannot invalidate the fixed and precise 

 laws of morphology." 



Eyes of Chitonidae.* — H. N. Moseley makes some important 

 additions to his earlier preliminary notice on the eyes of Chitons.l 

 He finds that tlie best method of getting sections is to decalcify the 

 shells rapidly with nitric acid, after hardening in strong alcohol. He 

 applies the term of " megalsesthetes " to the papilliform bodies of 

 Van Beneden ; the smaller bodies found in the micropores are called 

 micrresthetes ; they are small and knob-like, exactly of the structure 

 of the knobs of the macra3sthetes. He does not, with Van Beneden, 

 regard these organs of touch as homologous with the spines of the 

 girdle, or rather with the funicles by which these spines are supported, 

 jbut as having a quite peculiar and distinct structure. As eyes are 

 absent from the Solenogastres he suggests that the a3sthetes are 

 " organs developed originally in connection with the shells in the 

 Chitonidaj, still little differentiated in Chitonellus." As a compara- 

 tively late modification some of the megalsesthetes have in certain 

 genera been converted into eyes. As these genera are mostly inhabi- 

 tants of non-European seas it is difiicult to get satisfactorily pre- 

 pared specimens. The Sicilian C rubicundus might yield results of 

 value. 



Nervous System and Embryonic Forms of Gadinia garnotii-t — 

 H. de Lacaze-Duthiers describes the head of Gadinia as very 

 extensile and contractile, so that it and the lingual bulb suffer great 

 changes in position ; the oesophageal collar is proportionately large, 

 and the ganglia which compose it very distinct ; of these there are 

 three pairs, the first of which is dorsal and suboesophageal or cepha- 

 lic, the second which is abdominal or pedal, and the third sub-buccal 

 or stomatogastric ; these three pairs united by commissures and 

 connectives form two collars ; and in addition there is a third, formed 

 of an unequal number of ganglia, and consequently asymmetrical. 

 These ganglia, united transversely by a commissure which passes in 

 front of the oesophagus, form what the author has long since called 

 the asymmetrical centre ; it innervates the reproductive, respiratory, 

 and circulatory organs, as well as the mantle, or, in other words, all 

 the organs that are asymmetrical. Something analogous is to be seen 

 in the pulmonate Gastropoda, where, however, the asymmetrical 

 centre is formed of five ganglia. The auditory nerve is very long and 

 delicate, and excessively difficult to follow out ; like that of all gastro- 

 pods it arises from the brain and not from the pedal ganglion. The 



* Quart. Journ. Micr. Sci., xxv. (1883) pp. 37-CO (3 pis.). 



t See this Journal, iv. (1884) p. 728. 



X Comptes Rendus, c. (1885) pp. 146-51. 



