BRAIN 



217 



recognised even in the adult as a " brow-spot " : thus its 

 intracranial portion does not represent the entire epiphysis. 1 A 

 parietal organ appears to be entirely wanting in all Amphibians 

 with the possible exception of some few Anura, in which traces of 

 it have been described. 2 



-pa 



FIG. 165. LONGITUDINAL SECTION OF BRAIN OF AN EMBRYO OF Lacerta 

 vivipara x 26. (After K. von Kupffer.) 



ao, olfactory area ; bf, blood-sinus ; fro, olfactory lobe ; c, cerebellar commissures ; 

 ca, anterior commissure ; ch, superior (habenular) commissure ; ck, central 

 canal of spinal cord ; cp, posterior commissure ; cpa, anterior pallial (hippo- 

 campal) commissure ; C-/JQ, posterior optic commissure ; cpp, posterior pallial 

 commissure ; cs, spinal commissure ; <, swelling of optic chiasma ; e 1 , para- 

 physis ; hm, cerebral hemisphere ; hy, hypophysis ; in, interorbital septum ; 

 J (and >) ventricle of infundibulum ; opt, optic chiasma ; pa, parietal organ ; 

 pcA, choroid plexus on medulla oblongata ; K, hind-brain ; ro, optic recess ; 

 >/. sulcus intraencephalicus posterior ; tp, tuberculum posterius superius : 

 //-, torus transversus : rh, ventral flexure of medulla oblongata ; vc, valvula 

 cerebelli ; i*p, posterior medullary velum ; vt, velum transversum ; Z, epi- 

 physis. 



In the Gymnophiona the olfactory lobes and hemispheres are 

 relatively larger than in other Amphibians, and the hemispheres 

 overlap the posterior parts of the brain to a larger extent. The 



1 A rounded vascular body arising from the roof of the third ventricle and 

 representing a paraphysis (p. 200) has been mistaken for the epiphysis (Fig. 164, 

 A, ch. plx'}. 



2 A parietal foramen was, however, present in the Palaeozoic Stegocephali 

 and other extinct Amphibia. 



