180 LECTURE VIII. 



ganglions ('hypoaria,' fig. 53. w) * : their bulk is increased by added 

 grey matter, wliicli variegates their outer surface ; they are Avell 

 developed in the common Cod, in which, as in some other fishes, 

 they contain a cavity called ' hypoarian ventricle.' In some Salmo- 

 nidcE their surface is striated ; in some Ct/prinidce (Tench) they 

 are confluent; but commonly they are distinct, and have in their 

 inferior interspace a vascular medullary depressed sac (the ' hajma- 

 tosac,' fig. 53. o), usually oblong, as in the Cod, rarely bifid or cordi- 

 form, as in the Lump-fish, These prominences from the floor of 

 the mesencephalon, posterior to the infundibulum and hypophysis, 

 are peculiar to the brain of fishes, and, in their full development, are 

 restricted to the typical osseous member of the class ; they are absent 

 in the lowest, and disappear in the highest orders ; they are mere 

 rudiments, or are wanting, in the Polypterus, as in the still more 

 amphibioid Lepidosiren. 



The true vasculo-membranous infundibular downward prolongation 

 of the third ventricle exists in all osseous Fishes, and extends from 

 the anterior angle of the hypoaria where these exist : the infun- 

 dibulum is commonly short and thick, so that the hypophysis is 

 almost sessile, as in the Cod ; but in the Lophius, the infundibulum is 

 longer than the entire brain, and the hypophysis lies at the fore -part 

 of the cranial cavity, far in advance of the cerebral lobes, f In the 

 Cod the hypophysis (fig. 53. p) is a sub-spherical mass with an 

 irregular or slightly nodulated surface, almost half the size of the 

 human, so called, 'pituitary gland,' and well exemplifies the vast propor- 

 tional size of this constant appendage to the brain of Fishes. In the 

 Lepidosiren the infundibulum is wide, and the hypophysis a Avhite 

 flattened discoid body (fig. 54. />).| In all fishes it is richly supplied 

 with vessels, and is closely attached to the floor of the cranium ; but, 

 although its early development checks or modifies that of the cranial 

 vertebra3, it is not provided with a special chamber or ' sella.' The 

 prolongations of the fibres from the mesencephalon which expand 

 into the prosencephalic or proper cerebral lobes rarely shoAv any 

 preliminary development of ' thalami ; ' but the parts homologous 

 with those recruiting ganglia are constantly indicated by the attach- 

 ment of the conarium, or upper prolongation of the third ventricle. 



The conarium (figs. 50. 54, 55. tv) is as constant an appendage of 

 the encephalon in Fishes, as the hypophysis ; but is commonly only a 

 vasculo-membranous pyramidal sac continued from the third ven- 



* Analogous to the ' corpora mammillaria ' of the human brain, but not homo- 

 logous with them, as Arsaki (liii,), and Desmoulins (lxxviii. ) supposed. Cuvier 

 defines them as the ' lobes inferieurs,' xxiii. i. p. 318. 



f i.x. p. 56. t. ii. fig. 1. 



X The hypophysis is marked f/ in xxxiii. pi. 27. fig. 4., and is called 'mam- 

 millary body' in Lepidosiren annedens, \h. p. 3G1. 



