IN VEBTEBRATES AND INTERTEBKATKS. 3 



which is usually designated the " supraoesophageal ganglion," or, 

 after Lyonnet and Cuvier*, "the brain," 



This consists of a pair of neural masses, or " hemispheres," 

 confluent mesiallyfor one half of their longitudinal extent, before 

 and behind which confluent tract they are free. Each moiety 

 presents three lobes or enlargements, the smallest of which re- 

 ceives the antennal nerve, e, a second, the largest, the optic 

 nerve, j'^, the third the ocellar nerve, yt- From the oesopha- 

 geal surface of each moiety proceeds the tract or " commissure," 

 d, which, traversing its own side of the gullet, converges to and, 

 with its fellow, expands into the neural mass termed the " sub- 

 cesophageal ganglion," h. 



"With this neural mass are connected by origin or insertion 

 the nerves to the "trophi," i. e. the labrum, the mandibles, 

 the maxillae, the labium with its toDgue-like extension, and the 

 sense-organs called " maxillary " aud " labial palpi," together with 

 the complex muscles of these several parts. 



The properties of the vertebrate mouth, viz. taste and motions, 

 may be reasonably assigned to the foregoing invertebrate oral 

 organs: accordingly the nerves connected therewith, endowing 

 the mouth with the same characteristic powers and properties for 

 testing, seizing, and comminuting alimentary substances, I deem, 

 with their neural centres, to be homologous with those of like 

 endowments in the vertebrate animals. 



The part of the vertebrate brain to which, therefore, the so-called 

 " suboesophageal ganglion " in Invertebrates is analogous and, I 

 conceive also, homologous, is the basis of the epencephalon known 

 as the "medulla oblongata" (macromyelon), or so much of that 

 myelencephalous tract as may be in connexion with the trige- 

 minal and hypoglossal nerves — the neural machinery, to wit, for 

 the sensations and motions of the parts forming or being lodged 

 within, or furnishing secretions to, the vertebrate mouth. 



Through the difi'erent course of the gullet, in relation to cer- 

 tain nerve-centres in Vertebrates and Invertebrates $, a greater 

 degree of juxtaposition and concentration of those centres con- 

 nected with the special senses, and the neural mechanism relating 



* " Le cerveau proprement dit," Lemons d'Anat. comparee, ed. 1845, torn. iii. 

 pp. 305, 335. 



t I omit the filaments connecting the foremost minute mesial ganglion of the 

 " sympathetic " or " stomato-gastric " sj'stem with the above cerebral mass. 



\ Linnean Society's Journal, vol. xvi. p. 135, figs. 2 and 3. 



1* 



