PRIMORDIAL CRANIUM OF THE CAT 359 



are readjusted in the bony cranium, the cochlear capsules being 

 widely separated by a broad processus basilaris, and are them- 

 selves relatively smaller in the adult skull. 



Origin of the cartilaginous otic capsule. In discussing the ob- 

 servations which were made on the chondrification of the otic 

 capsule two questions of special interest present themselves: the 

 relation which the origin of the cartilaginous capsule as a whole 

 bears to the rest of the cranium; the original relation between 

 the pars cochlearis and the cartilaginous basis cranii. The first 

 question was raised by Huxley and there was sufficient evidence, 

 notwithstanding the crude methods of his time, for the ad- 

 vancement of the theory of intrinsic skeletal capsules for each 

 of the sense organs, ear, eye, and nose. Subsequent discovery 

 has tended to confirm the truth of this theory, the evidence 

 coming, as might be expected, chiefly from the lower vertebrates. 

 What mammalian crania will show must wait until the study of 

 successive developmental stages of species has been repeated by 

 modern methods. By the van Wijhe method, Noordenbos has 

 presented, recently, very strong evidence of the independent 

 origin of the cartilaginous otic capsule in Talpa; similar results 

 were obtained for rabbit, ox and pig. 



The second question has arisen in connection with Gaupp's 

 theory of the reformation of the cranial base to contribute a 

 supporting wall for the cochlear duct. There appears to be in 

 the reptiles a beginning development of the cochlear capsule 

 at the expense of the basal plate. Is the theory supported by 

 evidence from the mammalian chondrocranium and, what con- 

 cerns us here, does the development of the cochlear capsule in 

 cat throw any hght on the problem? So far as mammals are 

 concerned, it is convenient to consider these two questions to- 

 gether. First, it should be borne in mind that only the circum- 

 stances of chondrogenous development will be reviewed; the 

 concfitions of blastemal structure are here excluded. 



In regard to the pars canalicularis the evidence afforded 

 both by sections and van Wijhe preparations indicates that this 

 component of the ear capsule arises independently of other parts 

 of the cranium. There is some difference as to the form of the 



