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 Vespertilio mur intra 
and Rhinolophus ferrum-equinum, in another insectivorous bat, 
Vesperugo pipistrellus there is a moderately developed organ. 
They do not, however, appear to have made any study of the 
peculiarities of the organ. 
In the common Australian bat which I have studied ( Miniop- 
terus schreibersii, 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 
Jacobson'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, &c. 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 
