THE LATER DEVELOPMENT OF THE FROG 



173 



TABLE OF SOMITES, VERTEBRA, AND RELATED NERVES OF 

 THE TADPOLE (ELLIOT) 



Before the separation of the somites and lateral plate, the 

 latter shows traces of segmentation in the region adjoining the 

 somites, from which later the pronephros is formed (see below). 

 This region may therefore be termed nephrotome or intermediate 

 cell mass. These traces disappear, very quickly, and the lateral 

 plate itself is never segmented. The cavity of the lateral plate, 

 the general body cavity, gradually extends ventrally, and finally 

 divides the entire lateral plate into somatic and splanchnic 

 layers. Except in the extreme anterior and posterior ends of 

 the trunk, the cavities of the two sides meet and fuse across 

 the mid- ventral line, establishing a continuous body cavity and 



