PHARYNGEAL DERIVATIVES OF AMBLYSTOMA 645 



(p. 508) differs in several points from that of Amblystoma, 

 especially in being still in contact with the pharyngeal epithelium. 

 1 quote very briefly as follows : 



Der Suprapericardialkorper .... bestand in der einen aiis 

 einer kleinen, ampullenformigen Einsenkung des Pharynxepithels, 

 . . . Diese kleine Ampulle zeigte das gleiche Epithel wie die Pharynx- 

 wand, aiich Schleimzellen wiesen sich an ihr durch die Farbung aus. Von 

 hier aus setzte sich ein aus kleinen Zellen bestehender Epithelstrang, 

 welcher streckenweise ein feines Lumen zeigte, in ventraler Richtung 

 fort und er streckte sich so in den von Bindegewebe erfiillten Raum 

 zwischen Herzbeutel und dem (interbranchial) Muskel. Hier loste er 

 sich in zahlreiche kleiner Zellenstrange auf, welche mit Unterbrechungen 

 . . . verfolgen waren. Hier bildeten sie dorsal von der Wurzel 

 der 3 Kiemenarterie einen grossern Zellenhaufen. 



In another series of sections however, Driiner was unable to 

 find any trace of the ampullar structure. 



H. Late larval and early transforming stages. Although several 

 stages (40, 45 mm. and early transforming) were studied, the 

 postbranchial body changes but little in its morphological rela- 

 tions in any of them. A wax reconstruction of the body in a 40 

 mm. larva shows it a fairly compact structure, somewhat flat- 

 tened dorso-ventrally, and very irregular in outline (its total 

 length is now about 300 micra). As in the early larval stages, 

 the cephalic end insinuates itself between the lateral margin of the 

 aditus laryngeus muscle and the fourth afferent branchial artery, 

 the caudal end taking a more dorsal position. Internally it con- 

 tains several poorly defined intercommunicating cavities, which 

 run for the most part in a longitudinal direction. 



The body in the early transforming stage, although not changed 

 in position, is pressed closely against the medial wall of the fourth 

 branchial arch, by the growth of the now much enlarged aditus 

 laryngeus muscle. This flattens the body laterally so that the 

 lumina are obliterated throughout the greater part of its length. 

 At this stage the body is about 400 micra long, and as in the 

 previous stages, its anterior end is close to the wall of the peri- 

 cardium, its caudal end close to the floor of the pharynx. 



I. Late transforming stage. In this stage, the parts in the 

 immediate region of the postbranchial body, as well as the general 



