HOMOLOGY. 



5 



have been conducted with other than teleological aims : they 

 have led me to trace both the pineal and pituitary bodies, 

 their appendages and connections, or vi^hat 1 have termed 

 the " conario-hypophysial tract," from Man downward, until, 

 in Arnpliioxus, where the cerebral expansion of the myelen- 

 cephalon is too feebly indicated, the homologue of any part 

 of the tract in question has baffled my quest — unless the pore 

 or ciliated canal leading thereto may be in such relation. 



In the Mammalian series I have to observe that, in the 

 lower and smaller members, as the brain loses in relative size 

 and complexity, the pineal or conarial and pituitary or hypo- 

 physial bodies and connections show a relatively larger size, 

 with a less parenchymatous and a less interrupted tubular 

 structure than in the human brain. In the lower, if not 

 lowest, forms of the feathered class I have noted a character 

 of the basisphenoid which seemed to me to bear upon the 

 present topic : it is a median longitudinal groove leading to a 

 foramen opening into the seat of the pituitary body*. 



But leaving here the class of Birds in the present summary, 

 the proportions of the conario-hypophysial tract to the cerebral 

 hemispheres in Reptiles become greater, and a vascular chord 

 is continued upward from the hollow " pineal " part of the 

 tract, beyond the cleft between the pros- and mesencephalon, 

 to a contiguous opening in the bony cranial roof in a pro- 

 portion of the class, which proportion is greater in the extinct 

 members f. This "pineal" production perforates, as a rule, 

 the parietal bone, but in some species the suture between 



* See ' Memoirs on the Wingless Birds of New Zealand,' 4to, 18 78 : 

 Dinornis ehphantoims, pi. Ixxvi. fig. 4, 5 ; D. crassus, pi. Isxvii. fig. 3, 5; 

 D. ingens, pl. Ixxxii. fig. 3, 5 ; B. gravis, pl. Ixxxi, fig, 4, — in which the 

 foramen, not eustachian, is unusually and significantly large. 



t See ' Monograph on IcMhi/optenjgia,' Palgeontographical Society's 

 volume for 1881, 4to, p. 94, pl. xxiii. fig. 1,/^ also "Descriptive and 



