688 president's address. 



numerous and complicated ; its olfactory region is larger ; and its 

 cerebellum is both larger and more minutely divided by fissures, 



Symington has investigated the organ of Jacobson in Ornitho- 

 rhynchics'^ and in the kangaroo and rock-wallaby, I the result being, 

 briefly, that, whereas in the two latter there is not any wide 

 difference from what is observable in the Eutheria, in the former, 

 as in Echidna, the ox^gan is very extensively developed, running- 

 further forward than in the Eutheria, and with a complete tube 

 of cartilage from which a well-developed turbinated process passes 

 inwards. 



Kiikenthal'sJ researches on the dentition of Dideljihys are of 

 great interest and importance, as his genei'al results are most 

 probably applicable to all Marsupials, and have, moreover, an 

 important bearing on the question of the evolutional history of 

 the Mammalia. Kiikenthal finds that in the Marsupial, as in 

 Mammals in general, there are two rows of tooth-rudiments, au 

 inner and an outer, developed from the primitive dental fold. 

 In the higher Mammalia the inner set give rise to the permanent, 

 the outer to the milk dentition. In the Marsupial oue tooth 

 alone — the last premolar — is developed from the former of these 

 se[;S of rudiments, while all the remaining teeth are formed from 

 the latter. Hence the conclusion follows that all the teeth of 

 Marsupials, with the exception of the last premolar, are the 

 equivalents of the milk dentition of the higher Mammals. 



Thomas§ admits the justness of this deduction, but points out 

 that if the Marsupials are, as Kiikenthal supposes, primitively 

 diphyodont, and have become almost completely monophyodont by 

 a process of suppression of the teeth of the set corresponding to 

 the permanent series of the higher Mammalia, it becomes some- 

 what difficult to explain the case of Triconodon, oue of the earliest 

 of known Mammals, in which there is only one tooth with a 



* Proceedings Zoological Society, 1892. 

 + Journal of Anatomy and Physiology, XXVI. (1892 . 

 X Anatomischer Anzeiger, 1891 ; Annals and Magazine of Natural History, 

 1892. 



§ Annals and Magazine of Natural History, 1892. 



