74 



FREDERICK TILNEY AND LUTHER F. WARREN 



of the later stages in the cat is shown in figure 42, illustrating the 

 conditions in a 70 mm. embryo. Models by one of the authors 

 show the existence of this twofold structure in the cat as late as 

 120 mm. embryo. 



39 



25 



35 



Fig. 40 Mesial view of forebrain reconstruction of 30 mm. cat embryo. X 50. 

 The unshaded area shows the cut surfaces of the reconstruction, according to 

 Tilney, 1915 



2, chiasmatic process; 4, chiasm; 5, corpus interpedunculare; 7, epiphysis;9, 

 foramen of Monro; 11, infundibular stem; 12, infundibular canal; 13, infundibular 

 process; 20, lamina terminalis; 25, mammillary region; 32, post-chiasmatic emi- 

 nence; 33, post-chiasmatic recess; 34, post-infundibular eminence; 35, post-in- 

 fundibular recess; 39, dorsal sac; 40, recess of the infundibular process; 41 supra- 

 optic crest; 42, supra-optic recess. 



The most recent study of the pineal region in mammals is that 

 of John Warren, 417 in which he brings to a conclusion his excel- 

 lent series of papers upon the interpretation of this region of 

 the brain in vertebrates. Of the human embryo he gives the 

 following description (fig. 43) : 



