598 INVERTEBEATA CHAP. 



formed as a secondary outgrowth from a posterior zone of growth. 



f !- 



J> g g 43 g 



"o v- " o ii 



2 *i;; 



W .s '> c i? 



h c 6 - '? 



I 11^8 



S3 = i 



^3 fc-. r^ -^ c* 



5 to 



_, <u A 



>> Tl O 



*-; j y> ^. 



-S c * 



5 c S 



g S H 



s S 8 



^ ^ -s. 



B"S 



1 



? 



In many fish the tail is several times longer than the body, and it is 

 characteristic of the low place which Amphioxus occupies in the 



