IN VERTEBRATES AND INVERTEBRATES. 9 



ganglion, which is more distinctly divided into a fore and hind 

 mass. The first of these supplies the anterior or cephalic mus- 

 cular and tegumentary parts, the second the posterior or corporal 

 ones ; and from this division or cerebral centre are derived the 

 nerves of the acoustic organs developed or imbedded in the cor- 

 responding supporting cartilage*. 



The super- (h8em-)oesophageal body develops no peripheral lobe, 

 is in the form of a thick cord which sends forward nerves to oral 

 parts suggestive of an olfactory function, and, laterally, the large 

 short cords, swelling into ganglions, subserving the retinal supply 

 of the pedunculate eyes. 



The brain-space traversed by the gullet is wider than in the 

 Dibranchiates, the annectant tracts between the " supra-" and 

 " suboesophageal " masses are longer ; but their resemblance to 

 the (esophageal cords in the Articulates is still closer in the mo- 

 difications of the cephalopodal type of the nervous system, espe- 

 cially of its encephalic centres, which are seen in Aplysia and all 

 lower Mollusca. 



And here I need only to refer to the rich series of monographs 

 on this branch of comparative neurology, for which we are in- 

 debted to our fellow Member and labourer Mr. Robert Grarner, 

 of Stoke-upon-Trent f, still in enjoyment of health and intellectual 

 vigour ; also to another, whose loss we lament, the late Dr. Albany 

 Hancock, F.E.S.J 



In his admirable researches on the Nervous System of Insects, 

 Newport § discovered that "the nervous cords between the 

 ganglia included two columns," and that " the inferior column 

 alone goes to the formation of the ganglia, whilst the superior 

 lies upon them without any perceptible enlargement." Upon 

 this he founded his distinction of the " motor " and " sensitive " 

 columns in Insects as in Vertebrates. This, of itself, must weigh 

 in the question of the homology of the ganglionic cords of Arti- 

 culates with the myelon of Vertebrates ; and acceptors of such 

 homology gain by a determination of the corresponding surfaces 



* Macdonald, Anat. of the Nautihis umbilicatus, Phil. Trans. 1855, p. 279. 



t See his beautifully illustrated memoirs in the Transactions of the Linnean 

 Society, vol. xvii. (1837), and in the Transactions of the Zoological Societj', 

 vol. ii. (1835). 



\ By monographs in the publications by the Eay Society, in the 'Annals of 

 Natural History,' and in the ' Philosophical Transactions,' with his associate 

 workers Embleton and Alder. 



§ Philosophical Transactions, 1843, p. 243. 



