The Chondrocranium of an Embryo Pig. 201 



its whole length. Whether this difference is due to the difference 

 in the stages of development of the nasal capsules in the several 

 embryos or to more fundamental causes, I am, at present, not able 

 to say. 



The nasal septum, as stated above, forms the anterior continua- 

 tion of the interorbital septum or basal cartilage of the orbitotem- 

 poral region, the one passing gradually into the other. The nasal 

 septum undergoes no sudden increase in height nor diminution in 

 width immediately in front of the basilar cartilage of the orbitotem- 

 poral region, a feature so striking in Talpa, but present also, although 

 to a less degree, in Lepus, Homo and Semnopithecus. With the ex- 

 ception of its anterior quarter, it is thickest near its lower border 

 (Fig. 6). Its greatest height is in the middle region (Fig. 9) op- 

 posite the anterior ends of the fenestrse cribrosae, from which place 

 it tapers both anteriorly and posteriorly. Posterior to this highest 

 point its dorsal edge forms the crista galli, while anteriorly it 

 splits, the two dorsal parts then curving upward and outward to 

 form the tectum nasi. The extreme tip of the chondrocranium is 

 formed by the two capsules which project a short distance in front 

 of the septum. 



In the anterior part of the nose, a short distance within the nasal 

 opening there is a thin place in the septum. This was noticed by 

 Parker in Sus embryos, while Fischer found that in Talpa no 

 cartilage was formed at this point, but that the two chambers were 

 connected by an opening in the cartilaginous septum filled only with 

 connective tissue. Gaupp found a similar fenestra septi in Echidna. 

 Spurgat (189G) considers this one of the adaptations in connection 

 with the flexible snout, the absorption of a part of the cartilage a 

 short distance back from the end of the nose leaving the distal 

 portion more movable. In Erinaceus, ISTasua, Lutra and Canis, 

 there is also, to a greater or less extent, an absorption of the zone 

 of cartilage lying between the anterior ends of the membrane bones 

 (nasals and premaxillaries) and the tip of the nose. 



The processus maxillaris posterior, which in a number of forms. 

 Decker wrongly named processus uncinatus, is also present here. 

 It is probably the homolog of the processus maxillaris posterior of 



