606 FRANCIS M. BALDWIN 



3. Posthrancbial bodj^ 639 



A. Larvae 8 mm. long 640 



B. Larvae 9.5 mm. long 641 



C. Larvae 10-11 mm. long 641 



D. Larvae 13-15 mm. long 641 



E. Larvae 19-20 mm. long 643 



F. Lai;vae 26 mm. long 644 



G. Larvae 35-40 mm. long 644 



H. Late larval, and early transforming larvae' 645 



I. Late transforming larvae 645 



J. Postbranchial body of adult 646 



4. Carotid gland and epithelial bodies 646 



A. Transforming larvae 647 



B. Adult structures 649 



in. Review of the literature 651 



A. Concerning structures in Amphibians 651 



B. Concerning structures in other Vertebrates 652 



IV. General summary 667 



V. Bibliography 671 



I. INTRODUCTION 



The recognition, within recent years, of the parts played by 

 certain of the structures arising from the walls of the human 

 pharynx, in health and disease, renders these bodies of great im- 

 portance, and hence every fact which throws light upon their 

 morphology is of value. It was from such considerations that 

 the study detailed below were outlined, for, while a knowledge 

 of their development and structure in amphibia may have no 

 immediate practical value, the close relations of that group to the 

 ancestors of the mammals gives every addition to our knowledge 

 an interest which would not be expected with such groups as the 

 teleosts and birds. 



The literature of the subject, while not great, is rather difficult 

 to follow, because of the lack of unanimity of opinion as to ho- 

 mologies, and also from the conflicting nomenclature of the subject, 

 the same structures often having different names even in the 

 same minor group. In some groups pharyngeal derivatives are 

 found which apparently do not occur in the amphibia or at least 

 in the urodeles. These have not been considered here, and the 

 present work is restricted to the series of 'glands' et cetera which 



