PHYLOGENY OF THE PAL^OGNATH^ AND NEOGNATH^. 247 



NERVOUS SYSTEM. 



The Brain. 



Parker has shown that, compared with the brains of many Neofjnathw — Turkey, 

 Emu, Goose, Pigeon, — the cerebral hemispheres in Apteryx are proportionately of 

 large size, and further peculiiir is the way they overlap the cerebellum, in this respect 

 bearing a very close resemblance to the Passeres. This overlapping conceals the 

 grooves wliich mark the anterior region of the cerebellum, the hemispheres extending 

 as far back as the flocculi. The posterior grooves are visible superficially, as in other 

 brains. The pineal peduncle, in consequence of this overlapping, is inclined from 

 the vertical position backwards. 



The position of the thalamencephalou is also peculiar, in that this region is tilted 

 backwards, the lamina terminalis looking upwards, the foramen of Monro becoming 

 postero- instead of antero-dorsal. 



TuE Eye. 



The pecten is well developed in all the Pal(eognatha\ save Apferi/x. In 

 Dromceus the number of its folds is reduced to four ; in titnitJiio the lamellse are from 

 14-20 in numbei'. 



In Apteryx the pecten is generally believed to be wanting in the adult, though 

 present in the embryo. Dr. G. Lindsay Johnson, by a series of drawings recently 

 exhibited at a soiree of the Royal Society, has shown that this is not really the case. 

 The pecten is present in Jipteryx, though it assumes a peculiar form, being columnar, 

 not fan-shaped, and plicated. In all other birds the pecten has two or more plications 

 and is never conical — usually forming a vertical, plicated, densely pigmented septum 

 dividing the disc into a right and left half, although its base expands over it so that 

 very little of the disc is seen. The eye is small. Hence the apex of the pecten 

 penetrates the vitreous to a distance nearly equal to that of the posterior surface of the 

 lens from the retina. 



Dr. Johnson's researches in this direction have related almost exclusively to the 

 mammalian eye ; and they have been most fruitful in results, enabling him to demon- 

 strate a precisely similar " pecten "" in the eyes of several Mammalia, that of the 

 Golden Agouti — as he showed by means of drawings, exhibited at tiie above- 

 mentioned soiree in June of this year — bearing a most striking resemblance to that of 

 Apteryx. 



JaCOBSON's CARTir.AGES. 



These, according to Parker, are represented by a pair of vestigial rods ol cartilage 

 lying parallel to, and either immediately dorsad or slightly laterad of, the dorsal edge 



2 M 2 



