The Chondrocranium of an Embryo Pig. 185 



a quarter of the bulk of the entire capsule. This condition cor- 

 responds with the great development of the cochlea in the adult pig 

 (nearly four turns). The inner portion of the pars cochlearis is 

 a single cavity, but it is provided with a ridge, (Fig. 5, coch.) 

 largest next to the foramen acusticum, which runs spirally once 

 around the inside. This represents the beginning of the cochlear 

 formation. 



Sound-Conducting Apparatus. 



The ear-bones, or rather their, cartilaginous forerunners, will now 

 be considered, together with Meckel's cartilage and the hyoid arch, 

 which are connected with the ear-bones at an early stage in their 

 development. The ear-bones are located on the outer side of the 

 pars cochlearis and in front of the pars vestibularis. 



The Meckelian cartilages (Pis. Ill and IV, Meek, cart.) extend 

 forward in the mandibles until they meet and form a firm mandibular 

 symphysis. Throughout their whole length, except just before they 

 unite, they are nearly circular in cross-section, although their dia- 

 meters vary at different points. They do not continue in a direct 

 course from the malleolar portion to the symphysis, but each is 

 sigmoidally curved, the middle half sloping ventralward more sharply 

 than the end portions. Each cartilage forms at its posterior end 

 the irregular expansion which is later transformed into the malleus, 

 while between this and the pars vestibularis is the triradiate incudal 

 cartilage. Ventral to the mallear and incudal Aniagen is the posterior 

 end of the slender rod-shaped hyoid arch. In Sus this portion of 

 the arch (Reichert's cartilage) ends freely at this stage. Wliether 

 or not there is a connection between the crista parotica and Reichert's 

 cartilage at an earlier stage, I cannot say. In the adult tliere is 

 no indication of an osseous connection with the periotic ; in con- 

 nection with this the crista parotica is feebly developed, and the hyoid 

 arch is supported secondarily by the auditory bulla, which surrounds 

 and generally fuses with it. On the other hand, in most mammals 

 the tympanohyal (proximal end of the hyoid arch) is continued 

 directly into the crista parotica, which then forms a prominent ridge 

 external to the sulcus facilalis (cf. Cervus, Homo, Semnopithecus 

 and Lepus). Anteriorly the hyoid arches (Pis. Ill and IV) extend 



