zoo; 



covered by atrial epithelium pushed inwards by the gr^ 

 the gonad; within this, and completely surrounding the repro- 

 ductive organ, is a single layer of epithelium which is' t shown 

 by development to be ccelomic, Hence each gonad is surfoundbd 

 by a closed coelomic sac. -/ 



When ripe the inner walls of the gonadic pouches burst, and 

 the ova or sperms make their way into the atrium and thence 



i . 7U4. Amphioxus lancelolatus. .Segmentation 

 stage, (C) from above ; H, vertical section of G ; K, vertical 

 (From Korschelt and Heider, after Hatschek.) 



by the atriopore to the external water where 

 place. The laid eggs are covered by a thin 

 formed of flattened cells. 



Development. Only one polar body has beta 

 704, A). After impregnation the follicukr n 



ur-celled 

 stage I. 



takes 

 wane, 



Fig. 



