author's abstract of this paper issued by 

 the bibliographic service, november 18 



THE ORIGIN OF THE ULTIMOBRANCHIAL BODY AND 



ITS RELATION TO THE FIFTH 



POUCH IN BIRDS 



CHARLES EUGENE JOHNSON 



Department of Animal Biology, University of Minnesota 



TWO TEXT FIGURES AND TWO PLATES 



The authority on which the accounts in text-books of embry- 

 ology of the origin of the ultimobranchial body in birds are 

 based is the work of Verdun ('98) on the chick. According to 

 him, the uhimobranchial body arises from a diverticulum of the 

 pharyngeal wall just behind the fourth visceral pouch. He calls 

 this diverticulum the fifth visceral pouch, and he found it first 

 in embryos of 124 hours. It was not present in embryos of 96 

 hours, he states, and at this stage the fourth pouch also was 

 lacking. For an embryo of 148 hours he illustrates it as a cau- 

 dally directed sac-like outpouching of approximately the same 

 size as the fourth visceral pouch itself, at the base of which it 

 opens into the pharynx through a wide mouth. 



In a survey of the literature on the subject in the chick one 

 finds the accounts of the development of the ultimobranchial 

 body and its relations to the fifth pouch rather indefinite and 

 conflicting. Kastschenko ('87) found the so-called fifth pouch 

 in a chick embryo of four days (illustrated in his figures 11 and 

 14, plate 19). Again in an embryo of six days he recognized a 

 large 'bulbose Anschwellung' connected on one hand with the 

 fourth visceral pouch and on the other with the pharynx, which 

 "nichts anderes als die fiinfte Schlundtasche darstellt." This 

 fifth pouch, he states, has remained connected with the fourth 

 pouch during the elongation of* the latter and retains the con- 

 nection also at a later period, after the two thymus anlagen have 

 been separated from the pharyngeal wall. He refers to de Meu- 



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