484 
HOMOLOGY OF PALATINE PROCESS, 
figured his anterior paired vomers developing in Erinacexis: and 
the only difference in the mode of development of the palatine 
process of the premaxillary in the young marsupial is that in it 
the bony splint of Jacobson's cartilage is while developing united 
anteriorly to the premaxillary. 
There is one other bone to which reference need be made in 
this connection — the so-called " vomer " of the lizard. Most 
anatomists have regarded this as the homologue of the mammalian 
vomer. Kitchen Parker, however, though generally referring to 
the large paired bones in the front of the palatal region in the 
acertilian skull as "vomers," evidently later recognises their 
homology with the anterior paired vomers in Erinaceus, and not 
with the mammalian vomer proper, as will be seen from the 
passage already quoted. With this homology I entirely agree. 
It is universally admitted that the organ of J acobson in the lizard 
is the true homolgue of that in the mammal, and there can be as 
little doubt but that the cartilaginous supports, both being 
developments of the trabecular cornu, are also homologous, so 
that the homology of the bones developed as splints on the median 
sides of these cartilages in similar situations cannot well be denied. 
In lizards, moreover, the premaxillary has no palatine process, 
and the so-called vomer bears a similar relation to the pre- 
maxillary as does the palatine process in the mammal. In the 
snake this "vomer" passes up the septum nasi, and even slightly 
overlaps the capsules of Jacobson; but this is exactly what occurs 
in Oruithorhynchus, and to a less extent in some rodents. 
It will thus be seen that there is a distinct osseous element 
developed as a splint on the median side of the cartilage of 
Jacobson, which in lizards and snakes like the organ of Jacobson 
itself is well developed and distinct, but which in mammals, 
probably owing to the great development of the premaxilla in 
connection with the well formed incisor teeth, usually becomes 
early anchylosed with that bone, and in many cases even develop- 
ing in connection with it, forming its palatine process, only 
remaining distinct in a few forms such as Ornithorhynchus and 
Miniopterxis. For this ossification which in different forms has 
