ADTHOR 8 ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, DECEMBER 27 



BRANCHIAL DERIVATIVES IN TURTLES^ 



CHARLES EUGENE JOHNSON 

 Department of Zoology, University of Kansas 



FIVE PLATES (tWENTY-FOUR FIGURES) 



INTRODUCTION 



Studies on the branchial derivatives of reptiles have been 

 confined chiefly to lizards and snakes. The most recent work 

 on these groups is that of St. Remy et Prenant ('03-'04). . In 

 the former group, represented by the genera Anguis and Lacerta, 

 these authors found that a thymus body is formed by the second 

 and third gill pouches only. The derivative of the second pouch 

 is of variable size; whether it persists into the adult stage or 

 not they were unable to determine. The third pouch gives 

 rise also to a persisting epithehal body or parathyreoid. The 

 fourth pouch gives origin only to a transitory epithelial body. 

 The fifth pouch is of very rudimentary nature; it attains the 

 form of a small blind pocket which soon disappears without giv- 

 ing rise to derivatives of any kind. A right and a left ultimobran- 

 chial evagination is present in the early stages, but the left one 

 alone is destined to develop into a glandular organ; the right, as a 

 rule, very soon disappears entirely, but in one instance a rudi- 

 mentary ultimobranchial body was found on this side in an 

 embryo Anguis of 6 cm. length. 



In snakes, represented by the genera Coluber and Tropido- 

 notus, a somewhat different condition was found. In this 

 group the first and second gill pouches give rise to rudimentary, 

 transitory thymus bodies, that of the second being the larger. 

 The third pouch likewise produces a transitory thymus bud very 

 similar to that of the first or the second pouch, but in addition 



* Technical assistance for a part of the present work was made possible through 

 the research fund of the University of Kansas. 



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JOURNAL OF MORPHOLOGT, VOL. 36, NO. 2 



