572 ORGAN OF JACOBSON IN AN AUSTRALIAN BAT, 



this paper the authors call attention to the fact that the organ is 

 not invariably absent in the order, and comment on the curious 

 fact that though the organ is quite absent in Vesper tilio murinva 

 and Rhinoloj)hus ferrum-eqidnuin^ in another insectivorous bat, 

 Vesperugo 'pijnslrellus there is a moderately developed organ. 

 They do not, however, appear to hav^ made any study of the 

 peculiarities of the organ. 



In the common Australian bat which I have studied ( Minwp- 

 terns schrdbersii, Natt.) the organ is not only present, but is 

 unusually well-developed ; and furthermore it presents certain 

 features which distinguish it from the ordinary mammalian type. 



In my recent thesis have been recognised in the Placental 

 Mammals and Marsupials at least three types of Jacobson's 

 Organ, and of the third type two well marked varieties. In the 

 Marsupialia we have a simple generalised type which is moderately 

 closely related to Monotreme type as found in Echidna. The 

 organ in Rodents, on the other hand, is peculiarly specialised in 

 opening into the nasal cavity and not into Stenson's duct, though 

 in other respects it comes near to the Marsupial type. In all the 

 other orders of Mammals in which the organ has been examined, 

 so far as I am aware, a third type is followed. Here the organ 

 opens into Stenson's canal as in Marsupials, but the canal is 

 greatly developed in length and passes forwards, becoming merged 

 with Jacobson's duct. There is further a precurrent process of 

 JacolDson's cartilage on the inside of Jacobson's duct, and a 

 similar process on the outer side of Stenson's duct. These, on 

 passing forward, unite above and form a common cartilage for the 

 common duct. This is the type of the Dog, Cat, Sheep, (fee. In 

 the bat we have a variety of this type. The cartilages and ducts 

 are arranged in a somewhat similar way, but there is an absence 

 of the great elongation of the ducts, which in their mode of con- 

 nection with the nasal cavity, and with Jacobson's Organ, present 

 a much nearer approach to the simple Marsupial type. 



In Miniopterus, though the premaxillaries are fairly well 

 developed, they do not meet in the middle line, a condition 



