PRIMOKDIAL CRANIUM OF THE CAT 375 



and alisphenoid behind, both parts united in front in three of 

 the stages studied. Wincza's observations have since been con- 

 firmed for man by Levi ('00), Gaupp ('02) and Fawcett ('10); 

 for the dog by Ohnstead ('11). Noordenbos ('05), Voit ('09) and 

 Fuchs ('10) have seen the separating zone in Lepus. Noorden- 

 bos also found the ala temporahs a free process in the pig and 

 horse. A characteristic of the synchondrosis between ahsphe- 

 noid and basisphenoid of the cat described by Wincza, is its 

 obUque course from behind, forward and medial ward. Whether 

 the obUquity is a constant feature of the separating zone of the 

 ala temporalis in other forms studied by Wincza is not specfi- 

 cally stated. Figure 8 of Wincza's paper shows a cleft separating 

 the two parts in the polar bear, having the same direction as 

 the boundary zone in the cat. Mackhn ('14) found in a 40 mm. 

 human embryo that the connection between the lateral portion 

 of the ala and the processus alaris took place between the ven- 

 tral surface of the latter and the subjacent ala. 



In contrast to the type of independent ala temporalis there has 

 been observed another type, characterized by its continuity with 

 the basis cranii. Wincza saw no trace of a boundary between 

 basisphenoid and aUsphenoid in the chondrocranium of embryos 

 of the horse, pig, sheep and calf. Noordenbos, however, as just 

 stated, disagrees with the observation on the horse and pig; 

 he finds the ala temporalis in mole to be a process of the side 

 of the sella turcica. In Echidna, Gaupp identified the ala tem- 

 porahs in the small continuous process which springs from the 

 side of the sella turcica, laterad of the carotid foramen. 



From these records we learn that, in a ^^ariety of mammals, 

 the ala temporahs is more or less distinct from the rest of the 

 cranium, being separated from a basal process by a stratum of 

 some tissue other than cartilage, or even by a cleft of greater or 

 less extent ; whereas in others the ala is a simple process continu- 

 ous with the cranial base. Fm-thermore, Noordenbos, from his 

 own observations, recognizes two types of embryonic origin of 

 the ala tero.porahs in mammals; one type represented by the 

 mole, in which the ala ari.ses as a lateral process of the pole-plate; 

 the 'other type, represented by the rabbit, wherein the ala arises 



