BY R. BROOM. 481 



There is one interesting group of mammals — the CJieiroptera — 

 in which the condition of parts has not, I think, been ver}^ care- 

 fully observed, and from which we find considerable assistance in 

 the solution of the present problem. In the insectivorous bat 

 common in this district (JliniojHerus Schreibersii, Natt.) the 

 organ of Jacobson is well developed, but is unlike that of the 

 typical mammal in being unusually short compared with its 

 breadth. The premaxill?e are moderately well developed, though 

 they do not quite meet in the middle line, but they do not 

 possess even a trace of palatine process. The cartilages of 

 Jacobson are supported on the inner side by a small median bone 

 which is quite unconnected with either the premaxillae in front 

 or the vomer behind. It is situated immediately in front of the 

 anterior end of the vomer and clearly belongs to the same class 

 of bones as the vomer proper, though instead of being closely 

 related to the septal cartilage, it supports the cartilages of Jacobson 

 throughout almost their whole length. In front where the 

 capsules are moderately close together, a transverse section 

 reveals two bon}^ plates supporting them anchylosed in their 

 lower halves. Posteriorly the capsules are considerably apart, 

 and the bone is here found as a flat plate stretching from the one 

 to the other. 



In the common Australian flying-fox (Pteropus poliocephahis, 

 Tem.) the condition is very different, but peculiarly interesting. 

 The premaxilliTe are as well developed as in the Garnivora, though 

 they do not quite meet in the middle line. The organ of Jacob- 

 son as apparently in most insectivorous bats is here entirely 

 absent, though the recurrent cartilages are fairly well developed 

 as a pair of almost vertical plates. There is, however, no distinct 

 supporting bone as in Minioptf.riis, nor a trace of palatine processes 

 from the premaxillaries; but, on the other hand, the vomer is 

 well developed, and from it a process of bone passes forward into 

 the region corresponding to that occupied by the palatine process 

 in ordinary mammals, though, unlike the palatine process, it onlj^- 

 supports the posterior part of the cartilage. Whether in the 

 foetal condition this process is ever distinct, I have not had the 

 opportunity of ascertaining. 



