•250 DR R. BROOM ON THE 



pressed laterally, and instead of an inner and an outer process being sent forward to 

 support the ducts, we have these processes rudimentary, and retaining their attachment 

 to the nasal floor cartilage throughout their whole extent. Fig. 31 shows Jacobson's 

 duct and the naso-palatinc canal distinct, while the cartilaginous supports are seen as 

 outgrowths from the laterally compressed nasal floor cartilage. In fig. 38 the structures 

 are all seen in their usual relations. 



Cetacea. 



Through the kindness of Professor D'Arcy Thompson, I have been enabled to make 

 an examination of the snout of a young foetal Beluga. It has long been known that 

 the organ of Jacobson is absent in the whale tribe, but I was anxious to see if the 

 arrangement of the cartilages would give any evidence of the affinities of the group. 

 My work for the most part confirms Kukenthal's recent researches. Before conclusive 

 results can be obtained, however, younger embryos than any yet studied will have to he 

 examined. 



The peculiarities of the Cetacean are due to the nasal openings being shifted from their 

 normal situation in the anterior part of the snout to the upper region of the head. The 

 palatal region does not depart much from the normal type, there being even a small 

 papilla in the anterior part ; there is, however, no trace of a naso-palatine canal by the 

 side of the papilla. Fig. 39 represents a curved section cut so as to approximate to the 

 transverse in both the region of the nasal cavities and the snout. Above are seen the 

 two nasal cavities separated by the cartilaginous nasal septum, which passes right down 

 to near the palatal region where it rests on the vomer. On each side of the nasal 

 septum is seen a peculiarly developed cartilaginous plate. At its upper part it forms a 

 floor to the nasal cavity, but its chief part is closely placed against the nasal septum 

 which it supports down almost to its lower end. This cartilage is, with little doubt, the 

 true nasal floor cartilage, and its peculiar development is evidently the result of the 

 shifting of the anterior nares. It passes well forward in advance of the region of the 

 nasal cavities still resting by the side of the nasal septum, and ends about midway 

 between the nasal passage and the papilla. 



The only mammal in which I have met with a nasal floor cartilage at all comparable 

 with that in the whale is the horse, where, owing to a sort of rostrum being formed by 

 the well-developed premaxillaries, the nasal floor cartilage becomes laterally compressed 

 somewhat as in the Cetacean. Though the evidence afforded by the condition of the 

 cartilages is too slight to lead to any conclusions, so far as it goes it suggests affinities 

 with the higher Eutheria. 



