378 HOBEET J. TERRY 



middle process being thereby taken into the root of the ala. In 

 cat embryos of 17 mm., the ala temporalis, the derivative of the 

 mesenchymal alar element in relation to the Gasserian ganglion, 

 stands lateral to and in front of the anterior limb of the com- 

 missm^al element from which, however, it is separated by a layer 

 of mesenchyma (p. 329). Caudally the ala temporalis is sepa- 

 rated from the posterior limb of the commissural element by the 

 space which later results in the incisura lacera. The lamina 

 presents then an oblique Une of junction with the anterior limb 

 of the commissural element, extending from behind, forward and 

 medially. Later stages (23.1 mm.) as already described, show 

 along this Une a persistent sign of the separation of ala tempor- 

 alis and the arch made by the processus alaris and alicochlear 

 commissure, in the perichondral boundary zone first described 

 by Wincza. The anterior process, which in mole forms the 

 greater part of the ala temporalis, is entirely separated by an 

 interval from the anterior hmb and knee of the middle process 

 for a time; the alar element, which in the cat forms the entire 

 ala temporalis, is separated from the commisvsural element by an 

 interval (incisura lacera) only in its cauda.1 part. It will be re- 

 called that Wincza found in the polar-bear the alisphenoid sepa- 

 rated from the basi-sphenoid by a cleft which, as the figure shows, 

 runs from behind forward and medial ward. Also the same au- 

 thor found in the hedgehog a limiting zone in the posterior part 

 only of the ala temporalis. 



Apparently the alar element of the cat and the anterior lat- 

 eral process of the pole-plate of the mole are, in several respects, 

 comparable. The one real difference between the alar element 

 of the cat and the anterior process of the mole lies in the relation 

 of these parts to the side of the sella turcica : in the mole the ele- 

 ment in question is connected medially with the sella; in the cat 

 it passes medially into the commissural element, without inde- 

 pendent connection, if any at all, with -the side of the sella tur- 

 cica. There is a reduction, if not entire absence, of a medial 

 part of the alar element, next to the hypophyseal cartilage com- 

 parable with the root of the anterior process of mole. 



