THE HYPOPHYSIS IN REPTILES 243 



right side lies close to the wall of the pituitary fossa. In the next 

 section drawn (fig. 43) the dorsal surface of the large infundibulum 

 is in contact with the thin pars intermedia. The large anterior 

 lobe lies to the right of instead of ventral to the pars intermedia 

 and the infundibulum. Since the same relations are present in 

 late snake embryos, this is probably not an artefact as might at 

 first appear. The right side of the anterior lobe lies near the bony 

 wall of the pituitary fossa in the lower angle of which is seen the 

 cerebro-carotid artery. The left side of the pars intermedia lies 

 against the cranial floor. The caudal end of the hypophysis is 

 surrounded by the wall of the pituitary fossa (fig. 44). 



Discussion 



In reptiles, the first appearance of the hypophysis is a thick- 

 ened area of the epithelium of the oral roof and then a single 

 evagination of the latter. As Staderini ('03) has pointed out, 

 Gaupp ('93) was probably mistaken in describing a primary tri- 

 lobed hypophyseal anlage in lizards. Earlier investigators, with 

 the exception of Gaupp, believed the anlage of the hypophysis 

 to be a single evagination, and the tri-lobed condition to be of 

 secondary origin, and recent investigators of the hypophysis of 

 vertebrates also describe a single hypophyseal anlage. The 

 single evagination in turtles is triangular in outline and two 

 lateral buds are constricted from its sides. The lateral buds de- 

 velop relatively earlier in lizards, but as I have attempted to show, 

 are probably of secondary origin. In mammals and birds (Tilney 

 '13) and in pig (Miller '16) the lateral buds develop relatively 

 very much later than in reptiles. 



Salvi ('02) has attempted to prove that the lateral buds are 

 connected with the head cavities. That this is not true of turtles 

 is apparent from a study of my young embryos, in which, in 

 sagittal sections, the canal joining the first head cavities is caudal 

 to the hypophysis. A reconstruction of another young turtle 

 embryo also shows this dorso-caudal canal. Oppel ('90) and 

 Johnson ('13) figure no such relation as Salvi has described. 

 In turtles, Johnson figured the canal joining the head cavities 

 dorso-caudal to the hypophysis and distinctly separate from it. 



