1891.] ORGAN IN THK CROCODILIA. 155 



rnaxillse is effected. He asserts that in some of the forms he 

 examined he regarded the anterior paired vomers as the sole repre- 

 sentatives of the palatine processes of the premaxillae. In describing 

 some embryos, his language is only to be so construed as to show 

 that he regarded the latter as representing (Erinaceus, p. 149, Talpa, 

 p. 179, Galeopithecus, p. 253) a fusion of true palatine spurs of 

 the premaxillse with his anterior paired vomers so often alluded to. 

 In having declared that in the Mole the " anterior paired vomers . . . 

 are slightly separated from the palatine processes of the pre- 

 maxillaries " {loc. cit. p. 106), that in the same animal the " antero- 

 lateral vomers . . . have a very temporary and doubtful existence 

 independent of these processes of the premaxillaries " (p. 179), and 

 that while the palatine processes of the premaxillaries of the Shrew 

 in having " no separate antero-lateral vomer attached to them " have 

 " the same deficiency " as the Mole (p. 200), he has both involved 

 himself in a contradiction and shown that he was unable to draw a 

 sharp distinction between the palatine processes of the premaxillae 

 and his anterior paired (or lateral) vomers. The salient conclusions 

 which arise out of Parker's investigation are (a) that we can no 

 longer regard those structures ordinarily described among mammals 

 as " palatine processes of the premaxillae " as throughout homolo- 

 gous ; and (/3) that the latter are, in a number of cases, no parts of 

 the premaxillae at all, but rather referable to the vomerine category. 

 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 premaxillae of the adult 

 Ornithorhynchus as a combination of distinct elements \ 



All those mammals for which Parker has recorded the presence 

 of " anterior paired vomers " are long-nosed ^ Comparison of the 

 skulls of the 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 — occupy, that is to say, that of the 

 palatine lobe of Caiman niger {vo.'", fig. 2), in which the present 

 inquiry finds its focus. Putting all together, nothing is clearer than 

 that the vomers and palatine processes of the premaxillaries, which 

 have been, I take it, sufiiciently shown to be serial elements of a 

 common category, lie collectively within the area of the vomers of 

 the lower Amniota on one hand, and of the Crocodilian Caiman niger 

 on the other. Collating these facts with those before recapitulated 

 concerning the non-duplication and fundamental relationships of the 

 vomers in the lower Vertebrata, we may most reasonably conclude 

 that the bones referred to as anterior paired vomers and palatine 

 processes have "become separate by absorption" (most probably 



^ Auat. Schrifteu, Hamburg & Leipzig, Op. 31, 1883. 



^ Centetes, Ci^dofhAirus, Erinaceus, Galeopithecus, Manis, Orycteropu^, Bhyn- 

 chocyon, Fiorf.r, Talpa, Tatusia. 



