ORGAN OF JACOBSON IN THE INSECTIVORA^ 349 



is shown to be passing to the outer side of the jacobsott's dnct, 

 and Jacobson's cartilage coming to lie on the innet side of the 

 duct. The palatine process of the pfemaxilla is seen on one side 

 free from the pi-emaxilla. 



A few sections further back, as shown in iig. 7-, whieli re- 

 presents section 117, Jacobson's cartilage is united with the 

 lower part of the recurrent cartilage, and the naso-palatiiie canal 

 is seen to have opened into the nasal cavity. In the next four 

 sectioris, veins are seen to pass through two fair-si^ed Openings 

 in the cartilage about the level of the upper part of the palatine 

 process 



In fig. 6 is represented section 126-. Here the duct of 

 Jacobson's organ is just about to open out into the organ proper. 

 The palatine processes form flattened splints on the inner sides 

 of the cartilages of Jacobson. A portion of the secondary palatal 

 plate of the maxilla is seen in the section. 



The organ of Jacobson as distinct from the duct extends from 

 section 127 to section 178. The specimen examined is too young 

 to show clearly the arrangement of blood-vessels in connection 

 with the organ; Beyond section if 8 the organ is continued into 

 a glandular duct, which extends for ten more sections. 



Taljxt agrees with Gpnnuira in having feebly developed 

 glandular ridges ; in having practically no inferior turbinal in 

 that part of the nose in which is situated the anterior part of 

 Jacobson's organ ; in haV^lng the lower half of the nasal septum 

 converted into recurrent cartilages : and in Jacobson's orga.n 

 having a long duCt in front which opeUs into the anterior end of 

 the naso-palatine canal. It differs in a number of details, such 

 as the mode of opening of Jacobson's duct, the less forward 

 extension of Jacobson's cartilage, iia. the arrangement of the 

 blood-vessels of the organ, and in the better development of 

 the recurrent cartilages. 



There can, however, I think be little doubt but that Tcdjjci is 

 allied to Gymmlra and ma.y conveniently be left in the old 

 order Insectivora. 



I have made a series of sections of the snout of an adult Sorfx. 

 Unfortunately, the specimen wa,s not in the best state of preser- 

 vation, and, furthet", the structures are so extremely ossitied that 

 it is difficult to interpret some of the parts, and a young specimen 

 will require to be examined before olle can speak with any con- 

 fidence on the affinities. In certain features Sorex resembles 

 Centetes even more than it does talpa, and an examination of 

 the nose of a late foetus would probably reveal some interesting- 

 facts. 



The Organ of Jacobsdn in Centetes. (Pi. III. figs. 8-14.) 



The specimen examined was the snout of an adult Centetes 

 ecaudatus in fairly good preservation. It was sectioned by 

 hand. 



In the anterior part of the snout the median septum is well 



25* 



