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even more than in the Urodeles, one is impressed with the possibility 

 of this interpretation of the relations of the bones, for, in the frog, 

 the internal aperture lies in a reentrant angle between the vomer and 

 the palatine, as if it were actually forcing its way between them. The 

 non-dentigerous vomer of Parker's descriptions of Urodeles, it is to be 

 noted, has every appearance of being the homologue of the vomer of 

 Amia and Teleosts, and if it be the homologue of that bone it can 

 not be a breathing-valve bone. If, on the contrary, it be a breathing- 

 valve bone, the Teleostean vomer must be represented in the more or 

 less developed palatine process of the premaxillary. 



If then the maxillary breathing valve of fishes, and the bones 

 that develop in it, give rise to the secondary palate of the higher 

 vertebrates, this palate should not be found in Amphibians. And this 

 is exactly the case, according to generally accepted views. Seydel 

 (No. 40), however, considers that the first beginnings of a palate plate 

 are found in most Amphibians, it being represented in little dermal 

 flaps, partly supported by bone, that overlap, from their external edges, 

 the internal nostrils. In Ichthyophis, according to Seydel, there is 

 no trace, even, of this flap. As the lateral nasal groove of Seydel's 

 descriptions, which this flap covers, is said by him to be developed in 

 relation to Jacobson's organ, is it not perhaps possible that there is 

 here some indication that this organ and the olfactory organ are being, 

 in a way, enclosed in separate sections of a common groove, just as 

 adjoining organs of the lateral sensory canals are? The little flaps 

 described by Seydel might then have no relation whatever to the se- 

 condary palate. 



As against the above conclusions it should be noted that, in his 

 figures of Salamandra maculata, Seydel (No. 40) shows, in its proper 

 Teleostean position, a mucous fold that looks decidedly hke a breath- 

 ing valve, and it lies external to the internal nostrils. 



In those of the Stegocephali that are shown, in ventral view, by 

 Fritsch (No. 14), the internal nasal apertures lie postero - internal to 

 the so-called palatines. In snakes the internal nostrils have, according 

 to Huxley (No. 19), a similar relation to the palatines. In many 

 other reptiles, however, the nostrils lie anterior to the palatines, as 

 is well known (No. 11). Whether different steps in the process I have 

 assumed are here represented, or whether the so-called palatines of 

 reptiles are sometimes formed by one, and sometimes by the other of 

 the two components said by Parker to fuse to form the palatine of 

 Urodeles, I am wholly unable to judge. In the Crocodile, for example, 

 the breathing-valve bone must be represented in the palatal plate of 



