XIII 



PHYLUM CIIORDATA 



285 



of hearing not hitliorto met with. Bounded externally by the tym- 

 panic membrane and internally by the outer wall of tiie auditory 



A/cd.cbf. 



as 



'Jficd 



C/j:7 



c fitch 1,1^ 

 Cer.f/ fcrU ,^^ ,, c/>ff ^^ rfip/.v.2 



Atcd. obi 



Ch.pljc' 



Fig. 935.— Brain of Rana. A, from above"; B, from liolow ; C, from the side ; D, in longitudina 1 

 vertical section. ('<, cerebellum ; Ctr. //, cerel)ral hemispheres ; ch. pl.c^, anterior and 

 ch. plx", posterior choroid plexus (removed in A) ; com., commissures, the two in front the 

 anterior and hipjioca-mpal, the two above'thc xupt rior or hubcnulur and the poxlerior ; Cr. C, crura 

 cerebri ; Di, diencephalon ; for. M, foramen of Monro ; i, iter, or aqueduct of Sylvius ; inf, 

 infundibulum ; Med. obt, medulla oblongata ; Olf- I , olfactory lobe ; opt. ch, optic chiasnia ; 

 0/)(. /, optic lolie ; opt. v, iptic ventricle; j«((, stalk of pineal body ; j)i^ pituitary body; 

 Sp. cd, spinal cord ; v^, third ventricle ; vi, fourth ventricle ; / — A', cerebral nerves ; ISp. SUp. 

 spinal nerves. (From Parker's Praclirai Zoology. A — C, after Gaupp ; D, from AVieders- 

 heim's Comparative Analomy ; after Osborn.) 



