194 ON THE MORPHOLOGICAL CONSTITUTION OF 



the frog wbicli have their homologues in the stapes of the 

 mammal, and the columella, with its cartilaginous extremities, 

 in the bird and reptile. 



As the cartilaginous branchial arches of the tadpole, and 

 of the other Amphibia, are formed in the succeeding visceral 

 lamiuiie, it would appear to follow, as a necessary consequence, 

 that the suspensory or hyoidean arch of the amphibian, with 

 its inferior mesial element, and along with the auditory 

 ossicles, is homologous with the anterior or suspensory part of 

 the hyoid, along with the stirrup-bones in the mammal, and 

 with the corresponding structures in the bird and serpent ; 

 and that the first branchial arch of the amphibian, with its 

 corresponding iuferior mesial elements, are homologous with 

 the posterior horns and body of the hyoid in the mammal, and 

 with the posterior or suspensory horns, with the corresponding 

 mferior mesial elements of the hyoid in the bird. The so- 

 called posterior horns of the hyoid of the frog cannot, there- 

 fore, be the homologues, as Professor Owen's statements might 

 lead us to infer, of the posterior horns of the hyoid of the 

 mammal or bird. The posterior horns of the hyoid of the 

 frog are the remains of its posterior pair of branchial arches, 

 or enlargements of the posterior angles of its basi-hyals. 

 They are developed therefore in its posterior visceral laminse ; 

 while the posterior hyoidean horns of the mammal and bird 

 are developed in the third pair of visceral laminae. 



As the skeleton of the hyoidean and branchial apparatus 

 of the fish is developed in the form of a series of inverted 

 arches in the corresponding visceral laminse, from the second 

 inclusive, we are obliged to conclude that its hyoidean arch is 

 the homologue of the stylo-hyoidean arch, with the stirrup- 

 bones — or second post-stomal arch — in the mammal ; and of 

 the corresponding portion of the hyoidean apparatus in the 

 bird, with the columella ; and of the entire hyoid in the ser- 

 pent, with the columellae ; and that the first branchial arch in 



