25-i ANNALS NEW YORK ACADEMY OF SCIENCES 



A. J. Brown, The Development of the Spine in the Cat. 



J. T. Nichols, On Peimaeily Unadaptive A^^aeiants Among 



Veetebeates. 



SUMMAEY OF PaPEES 



Dr. Kernan stated that the chondrocranium presents at this stage 

 fairly complete development of the base of the skull in the region of the 

 posterior and middle fossge. There is no skull floor to the anterior fossa. 

 The lateral occipital regions are united to the basal region by two roots 

 which embrace the hypoglossal foramen. On the left side this foramen 

 is partially subdivided. There is some evidence in this embryo for the 

 view that the vertebrse entering into the formation of the occipital region 

 are of the atlas type. By this hypothesis is best explained the subchordal 

 position of the basioccipitaL and the relations of the suboccipital nerve 

 and the costal and transverse processes of the occipital vertebra to the 

 condyle. The paraoccipital process and the lamina alaris of the lateral 

 region may be analyzed on the evidence found in this fcetns into the 

 costal and transverse process of the occipital vertebrae. 



The otic capsules are well developed and they form with the parietal 

 plates which surmount them a considerable part of the side wall of the 

 skull, which contrasts markedly with their basal position in the adult. 

 In the orbito-temporal region the sphenoid body is a solid mass of carti- 

 lage. There is a well developed dorsum sellse, and sella turcica. The 

 lamina hyochiasmatica, which in earlier embryos is on a level with the 

 floor of the sella turcica, is elevated. The optic foramina are not yet 

 surrounded by cartilage, the alse orbitalis being unconnected with the 

 prsesphenoid. There are well developed alse hyochiasmatica free from 

 both prsesphenoid and alae orbitales. 



The alas temporales show separation into two parts, the processus alaris 

 related to the basisphenoid, and an independent processus ascendens. 

 The processus alaris is extended to the cochlea by a commissura ali- 

 cochlearis. The foramen rotundum is complete, the foramen ovale only 

 indicated. 



In the ethmoidal region the septum nasi is well developed. The nasal 

 Avails, however, are merely small plates of cartilage with only slight in- 

 rolling of the ventral edges to indicate the maxillo-turbinals. There is 

 no nasal roof or floor. 



Ossification has begun in two bones only, the maxilla and mandible. 



Meckel's cartilage is a massive structure, continuous dorsally with the 

 malleus Avhich shoAVS manubrium and caput. The incus shows all its 



