The pronephros of Chrysemys margiuata. 



77 



In Fig J (right side) the glomus is simple, unbranched, and 

 separated from the nephrostome of a pronephric tubule by the remains 

 of the nephrotome. On the left side the subdivision of the glomus 

 is shown, and a bloodvessel supplying it from the aorta. 



Textfig. K shows (right side) a pronephric tubule in the posterior 

 region of the pronephros opening into the coelom just where the 

 nephrotome opens. The glomus now projects into the enlarged lower 

 end of the nephrotome, and since this space is segmental the glomus 

 will be represented in it by an internal glomerulus. The tendency 

 of the lower end of the glomus to fuse with the somatic mesoderm 

 beyond the nephrostome is also shown. On the left side in this 

 figure the relations of a typical mesonephric tubule are indicated, — 

 glomerulus, Malpighian capsule, and tubule opening into the pro- 

 nephric duct. 



prot sp. cd gl gis 



cl. ao pr. t pr. d ms. f 



Textfig. L. Model showing the transition from pro- to mesonephros. 



Textfig. L is a modification of one of Felix's excellent dia- 

 grams. It attempts to illustrate the change from the pronephric to 

 the mesonephric condition. 



Summary and conclusions. 



1. The rudiment of the kidney in Chrysemijs is in the form of 

 a continuous "'primitive kidney groove" arising as a somatopleuric 



