The Chondrocraninm of an Embryo Pig. 169 



I will here take the opportunity to express to Professor Gaupp 

 my sincere appreciation not only for the use of his extensive series 

 of sections, but also for his very valuable help and suggestions. Dr. 

 Max Voit I wish to thank for the use of his Lepus reconstruction 

 and for the assistance which he has rendered me. And for the loan 

 of the reconstructions of the Semnopithecus, Macacus, Tarsius and 

 Talpa skulls, and also for the series of sections from which the Talpa 

 reconstruction was made I wish to express to Professor Eugen 

 Fischer my sincere thanks. 



The Skull as a Whole. 



The form of the primordial cranium of the pig represents well the 

 generalized mammalian type of chondrocraninm. 'No part is markedly 

 underdeveloped and no part is greatly overdeveloped at the expense 

 of the surrounding portions. 



As a whole, the chondrocraninm at this stage of development, i. e., 

 in an embryo 30 mm. long, resembles a pear in shape, Avith the small 

 end anterior, forming the nasal region, and the large end posterior. 

 The large brain-box is widely open dorsally, a feature characteristic 

 of the anmiotes. Later this region of the skull is completed by the 

 formation of the large roofing membrane bones, the frontals and 

 parietals. Veutrally the general contour is completed by the man- 

 dibular, hyoid and branchial arches. The brain-case is large and 

 extends forward over the posterior half of the nasal capsules, forcing 

 the fenestra) cribrosfB from their primitive vertical j^osition into a 

 horizontal one. Its side walls are formed by a broad continuous 

 plate of cartilage on each side, thus standing in sharp contrast to 

 the condition in similar embryos of man and the primates, in which 

 this region is very rudimentary. The nasal capsules are of moderate 

 length, not long as in Talpa, nor short as in man. Taken as a whole, 

 the chondrocraninm is complete except for some minor details. E'one 

 of the cartilaginous bones {Ersatzhnoclien, Gaupp) have as yet begun 

 to ossify. Some of the membrane bones have not yet appeared and 

 the others are only in the very early stages of their formation ; con- 

 sequently they have not been included in my reconstruction (Pis. 

 I-IV). With the exception of the mandibular, hyoid and branchial 



