SKELETON AND LARYNX OP XENOPTJS AND PIPA. Ill 



of the third and fourth, and the hyoglossal foramen as a second- 

 ary fenestration in the basibranchial cartilage. In none of these 

 respects do my observations accord with his. 



General Conclitsions, and Discussion op the 

 Affinities op the Aglossa. 



The most important outcome of the study of the development 

 of the hyobranchial skeleton which forms the subject of the pre- 

 ceding section is the demonstration of the fact that the wings of 

 the adult skeleton cannot be regarded as the derivatives of any 

 particular branchial arches, any more than can the two lateral 

 processes of the body of the hyoid, lying between the anterior 

 cornu and the thyrohyal, in the frog, which, as Gaupp (14) has 

 so admirably shown, are developing independently, while the 

 branchial arches are becoming absorbed. There is, it is true, a 

 great temptation to homologize processes and projections of adult 

 skeletal parts with structures of larval significance, but it is only 

 by resisting the temptation that a due regard for observed fact 

 can be assured. Careful inspection of the evidence upon which 

 Parker bases his deductions shows it to be of the most scanty 

 description, and discloses the fact that the homology he establishes 

 between the alae and the first two branchial arches, and between 

 the thyrohyals and the third and fourth, is conjecture rather 

 than a legitimate conclusion based upon the information in his 

 possession. Cope does not accept Parker's interpretation of these 

 structures, but it is extremely difficult to discover what his own 

 views really are, for while he copies (7. PI. 76. fi.g. 1) Parker's 

 figure of the hyobranchial skeleton of Xenopus (33. PI. 58. fig. 5), 

 and marks the wings ch. 1 and the thyrohyals ch. 2, yet on p. 252 

 he states that the Aglossa have the ^MrJceratobranchials greatly 

 elongated, — and this in spite of his generalization (p. 234) that 

 the thyrohyal of Salientia is the fourth, ceratobranchial. The 

 relations of the geniohyoid muscle point in the direction of the 

 alse being homologous with the lateral cartilages in front of 

 the thyrohyal (processus postero-lateralis, Gaupp, 14) which 

 attain such an exceptional length in JBonibinator, Felohates, and 

 Pelodytes. The anterior position, however, which the alse 

 occupy during development rather shakes one's faith in this 

 determination. 



The morphological significance of the thyrohyals in Auura 



