248 DR R. BROOM ON THE 



elements which are derived from the cornual cartilages all distinct. The section is made 

 in a plane a little behind the point where the naso-palatine canal opens into the nasal 

 cavity, and the palatine process has just become detached from the premaxillary bone. 

 The nasal floor cartilage proper is seen divided into an inner and an outer part, and at 

 the outer and lower corner of the naso-palatine canal is the remains of the outer canal 

 cartilage. Though in this type this little cartilage which supports the outer wall of the 

 canal is quite unconnected with the outer part of the nasal floor cartilage above, a com- 

 parison with the condition in Miniopterus, and especially with higher Ungulate types, 

 leaves little doubt but that it is morphologically a part of the outer nasal floor cartilage. 

 Beyond the plane of fig. 27 the inner part of the nasal floor cartilage proper unites with 

 the lower part to form Jacobson's cartilage, which now presents an appearance similar to 

 that in the hedgehog. 



Ungulata. — Notwithstanding the numerous points in the anatomy of the Ungulates, 

 which would seem to mark them off from the rest of the Eutheria as a well-defined group, 

 it is remarkable that in the relations of the organ of Jacobson and its cartilages there is 

 the closest agreement even in small points of detail with the condition found in other 

 higher Eutherians such as the Carnivora and Insectivora. The agreement is more marked 

 than between the Polyprotodont and Diprotodont Marsupials, and one is forced to the 

 conclusion that there is a more intimate relationship between the Ungulates and some 

 other of the so-called orders of the Eutheria than is at present believed. 



The different groups of Ungulates seem to be related to each other in much the same 

 way as are the Chiroptera, Insectivora, and Carnivora ; and in the types which have been 

 examined so far we find evidences of a parallel development, the pig representing the 

 simpler condition and the cow the more specialised. 



Sus. — The general anatomy of the snout of the pig has been fairly well illustrated 

 by Parker, but he has not entered upon the details of the anatomy of the structures 

 related to the organ of Jacobson or the naso-palatine canal. I have myself examined 

 the snout of a foetal pig (head length 19 mm.), which will be found to illustrate fairly 

 well the Ungulate type in its simplest form. On the whole there is a marked agree- 

 ment with the condition in Miniopterus, except that the outer nasal floor cartilage and 

 the anterior process which it normally gives rise to is likewise undeveloped. In fig. 28 

 we have a section through the point of entrance of the naso-palatine canal. By the 

 side of the base of the septum is the inner part of the nasal floor cartilage. Above the 

 upper part of the naso-palatine canal, and towards its inner side, is the well marked 

 anterior process of Jacobson's cartilage, and between this and the nasal floor cartilage 

 and a little internally is situated the palatine process of the premaxillary. The close 

 agreement with Miniopterus will be evident on comparing this figure with fig. 19. In 

 fig. 29 we have the condition of parts a little further back. Here Jacobson's cartilage 

 is complete, the anterior process being in contact with the upper part or nasal floor 

 cartilage exactly as is seen in Miniopterus (fig. 20). On the one side the duct of 

 Jacobson has just become separated off from the naso-palatine canal, and on the other 



