BY R. BROOM. 
479 
An examination of the early development of the parts shows 
that this close connection is not accidental, but that the support- 
ing bone is developed as a splint to the cartilage. If a mammary 
foetus of the common Phalanger (Trichosunis vu/pecula) 18 mm. in 
length be examined, it will be found that the bod}^ of the pre- 
maxillary is already fairly well ossified. The recurrent cartilages 
will be seen in section as two plates, slightly diverging below, 
lying on either side of the middle line below the base of the 
cartilaginous nasal septum. About the middle of the inner side 
of each recurrent cartilage and close to it is a tract of active 
cells, in the centre of which is a very delicate spicule of bone. 
This spicule, it must be admitted, is directly connected with the 
premaxillary, though as the tract of bone-producing cells in con- 
nection with the recurrent cartilage is practically similar to that 
which a little posteriorly lies around the base of the septum nasi 
and gives rise to the vomer, it is highly probable that there is a 
distinct osteogenetic tract in connection with the recurrent 
cartilage, and that owing to the early development of the pre- 
maxillary it is prematurely ossified by invasion from that bone. 
In Perameles and Dasyurus the recurrent cartilage tract is 
similarly ossif'ed by a bony process from the premaxillary. In 
many of the higher mammals (e.g., Krinaceus, Tatusia) it would 
appear that the ossification in connection with the recurrent 
cartilage maintains for some time its independent existence, 
though uniting later with the premaxillary to form its palatine 
process. In a few mammals (e.r/., Omithorhynchus and Miniop- 
terus) the ossification remains as a distinct bone throughout life. 
Prof. Kitchen Parker,* who has done more than anyone else 
to elucidate the development of the skull, does not seem to have 
arrived at any certain conclusions with regard to the nature of 
the palatine process of the premaxillary. His researches show 
tha.t he discovered supporting the cartilages of Jacobson a distinct 
bone which he called the "anterior paired vomer," but it is 
probable that, as Howes has pointed out, in trying to draw a 
* Loc. cit. 
