146 ON THE "dumb-bell-shaped" BONE IN ORNITHORHYNCHUS, 



theless, this inability can only be regarded as manifested in certain 

 cases, and Howes himself accepts from Parker certain conclusions 

 on this subject which he sums up as follows : — " (a) That we can 

 no longer regard those structures ordinarily described among 

 mammals as 'palatine' processes of the prercaxillse as throughout 

 homologous ; and (6) that the latter are, in a number of cases, no 

 parts of the premaxillse at all, but rather referable to the vomerine 

 category ;" and he adds that " in his discovery of the complex 

 nature of the (non-pathological) premaxilla of mammals Parker is 

 at one with Albrecht, who has shown that there is reason for 

 regarding the premaxillse of the adult Ornithorhynchus as a com- 

 bination of distinct elements." The author then proceeds as 

 follows : — " All those mammals for which Parker has recorded 

 the presence of 'anterior paired vomers ' are long-nosed. Com- 

 parison of the skulls of adults with those of the young as figured 

 by him, will show that while the bones in question may in some 

 cases pass over to the true vomers they more generally remain 

 exclusively related to Jacobson's organ, which they ensheath in 

 the form of the so-called premaxillary palatine processes, and their 

 products of fusion and metamorphosis lie, for the most part, 

 within the area of the latter as ordinarily described." I have 

 quoted at this length from Professor Howes' valuable paper 

 because it appears to me that the condition in OrnithorhyncJtus 

 may be easily interpreted in the light of the last few sentences. 

 Ornithorhynchus is a long-nosed mammal whose 'anterior vomers' 

 have fused together in development without uniting with any 

 other osseous element. Posteriorly they preserve an intimate 

 relation to the ventral edge of the septum nasi, while anteriorly 

 they constitute exclusively the osseous investment for the carti- 

 laginous capsules of the organs of Jacobson. 



In view of Howes' statements above quoted, and of his further 

 dictum that " the vomers and palatine processes of the premaxil- 

 laries have been sufficiently shown to be serial elements of a 

 common category," it is not strictly accurate to regard the 

 vomerine view of the dumb-bell bone as really a novel one. But 

 I am unaware that anyone has ever explicitly applied this inter- 



