BRAIN 



93 



That this idea is unsound seems clearly t. In- indicated \>y such 

 series of stations ;is that shown in l-'i^. f>.">. AJB 8 mai t.i of fact it 



f>4. Sagittal sections through the brain o! 



ch. 



(After Kupffer.) 



A. :;-3 mm., embryo; B, 7-8 nun. ; C, 10 mm. ; 1), 27 mm. ; E, 70 mm. tvc, ci>ivl>.-llum ; />, optic 

 chiasma ; /. rxtrinal rcUnlrrm ; li.c, lialirnulai- cnmmissiu-c ; inf. int'iindiliuliim : .V, cavity d' mi'srii- 

 cfj>h;ili>n : .V. imtuchonl ; n.ji, auti-rinr ncuropore ; p.c, iwstt-rior (-(immissurc ; i>in, piiifal or.^iii ; Rh, 

 cavity dt' ilmnibi'iicrplialiiii ; t.". tectinn ujitii-iiiii ; r, rclum trunsrerxinii ; r.\\. fourth vi-utriclf. 



seems probable that very pronounced flexure of the brain, such as is 

 seen in the developing Elasmobranch, is to be regarded as a secondary 



