565 



which separates the second vagus arch from the trunk of the embryo. 

 This posterior cleft lies fifteen sections beyond the plane of the 

 section figured. 



Fig. 9. Cross-section through the Anlageu of the suprapericardial bodies in an 

 embryo 15 mm long, cl 4 fourth branchial cleft (counting the hyomandibular). pc 

 •pra«cartilage cells, sp b suprapericardial body. X vagus ganglion. 



The view of van Bemmelen (loc. cit.) that the suprapericardial 

 bodies may be regarded as rudiments of a posterior pair of gill clefts 

 is not supported by their development in Necturus, since they arise 

 from the floor of the branchial chamber as some distance anterior 

 to the posterior cleft. 1 have therefore preferred to retain the 

 appellation by which van Bemmelen designated the bodies in question, 

 rather than to adopt that introduced by Maurer. In Necturus they 

 are „suprapericardial", but not "postbranchial". 



In later development the suprapericardial bodies are still found 

 near the place of their origin, although somewhat farther removed 

 from the floor of the branchial cavity. Each becomes closely applied 

 to the posterior wall of the vein which forms on either side of the 

 embryo the trunk in which the veins from the two posterior 

 branchial (vagus) arches unite before entering the heart. In a specimen 

 46 mm in length, the suprapericardial bodies are composed of several 

 vesicles. 



