ORGAN OP JACOBSON IN THE INSECTIYORA. 351 



palatine canal, but differs from both in the anterior part of 

 Jacobson's cartilage being less developed. It differs from both 

 in the greater development anteriorly of the inferior tnrbinal. 

 It resembles Gytnymra in having a single large blood-vessel along 

 the outer side of the organ. In the loss of the upper part of the 

 septal cartilage, it agrees with Sorex. I know of no other form 

 besides Centetes in which the lower part of- the septal cartilage is 

 completely surrounded by the vomer, as it is a little behind the 

 plane of Jacobson's organ. 



Whether Centetes should be placed with Gymnura and Talpa 

 in the order Insectivora, or placed in a separate order of the 

 Coenorhinata, the evidence from the structures in the nose does 

 not conclusively show, and it will therefore be well at present to 

 leave Centetes and its allies in a very distinct family or suborder 

 of the Insectivora. 



The Organ of Jacohson in Ohrysochloris. (Plate lY.) 



I have examined the organ and its relations in a newly-born 

 Chrysochloris hottentota, and a somewhat older Ghrysochloris 

 as'mtica. The former had a head-length of 12 mm., and the latter 

 a head-length of 16 mm. 



Fig. 1 represents section 40 of the nose of the newly-born 

 Chrysochloris hottentota. The median septum is slender ; the 

 alinasals are very wide. In the general arrangement of the 

 cartilages, and in the mode of opening of the naso-lacrimal 

 duct, the agreement with Tuj)aia is fairly close. 



Fig. 2 represents section 47. It will be unnecessary in the 

 present paper to discuss the morphology of the small cartilages 

 of the nasal valve, but this section shows a remarkable recurrent 

 process from the outer border of the alinasal. The only other 

 mammal I know of which possesses a similar structure is 

 Echidna. 



In fig. 3, which represents section 55, the most anterior part 

 of the premaxilla is cut through. The alinasal is continuous 

 with the anterior nasal-floor cartilage, and a very sharp fold 

 passes into the inferior turbinal. 



Fig. 4 represents section 64. Here the lower part of the 

 premaxilla is cut across as well as the lateral. The nasal-flooi 

 cartilage is no longer connected with the alinasal. The septal 

 cartilage shows the first indications of separating into upper and 

 lower parts. 



In fig. 5, which represents section 69, we see the division of 

 the septal cartilage into upper and lower parts, and the com- 

 mencing division of the lower into the two recurrent cartilages. 

 In this and the previous sections, the great encroachment on the 

 nasal cavity by the folding of the mucous membrane is seen to 

 be in marked contrast to the condition seen in 'faljya, Gyinnura, 

 and Centetes. 



Fig. 6, which represents section 86, cuts through the first 



