374 WALTER E. CAMP 



the epithelial derivatives of the pouches, which come to lie near 

 the thyreoid. He agrees with De Meuron, however, that the 

 postbranchial bodies in Anura are homologous with the supra- 

 pericardial bodies of selachians. He leaves entirely undecided 

 the question of the homology of the postbranchial bodies and 

 the derivatives of the fourth pouches in birds and mammals. 

 The unilateral development of the body in urodeles, and its 

 rather marked variation in structure from that found in Anura, 

 suggests to Maurer that possibly, in urodeles, the postbranchial 

 body represents a remnant of the ductus oesophago-cutaneous 

 of Bdellostoma. 



Piatt ('96), working with Necturus, described the supraperi- 

 cardial bodies as small vesicles arising from the ventral pharyn- 

 geal wall, between the fourth and fifth branchial clefts on either 

 side. They become separated from the pharynx but retain 

 their primitive position and show no fusion with the thyreoid. 

 The position of the bodies in Necturus, according to Piatt, 

 opposes the view of van Bemmelen that they are to be regarded 

 as rudimentary clefts and also the conception of Maurer that 

 they are postbranchial structures. 



In the tunicates Giard ('98) considers the epicardial tube 

 homologous with the postbranchial body, an homology of the 

 same nature as that of the endostyle with the median thyreoid. 



Greil ('05) opposes the view of Maurer that the supraperi- 

 cardial body in amphibia is postbranchial. By reconstructions 

 of the branchial region of the foregut in Hyla he found that the 

 anlage of the sixth pouch appears on either side as a shallow 

 outpouching of the lateral pharyngeal wall, caudal and slightly 

 medial to the fifth pouch. The thickened epithelium of the 

 ventral portion of this rudimentary sixth pouch develops into 

 the ultimobranchial (suprapericardial, postbranchial) body. 

 The bodies develop symmetrically on the two sides. The dorsal 

 and medial segments of the sixth pouch form a cord of cells 

 which runs caudalwards and unites with the gut. The ultimo- 

 branchial body is completely separated from the pharynx and 

 contains a small central lumen. Greil believes that Maurer, 

 overlooking the remaining segments of the sixth pouch, de- 



