Text-fio. 19. 





ur—^Sfti. 



St 



\ .::^. V 





.^4 



Itit: 









-AC 



■■''■"i^v5^WviS«^"*' 



Section throut;li the saiue region of an older enilnyo. l>ut taken almost 

 at right angles to the section drawn in Text-fig. IH. Tlie coelom has 

 increased in size and is beginning to extend dorsally between the body- 

 wall and the stomach. The secondary kidney is cut longitudinally to 

 show its vacuolated structure and the duct opening into the mantle- 

 cavity. 



Text-fig. 20. 



f??k .•^•'^."i:: V::.;-::.:,. ■ ^/ 





L.Ir 



*"\.* -.S'^" ''■ ■ 





'■■S^^^gt' - . ^_^,..Aii»siiC'»a«j 



Transverse section through an embryo at a stage corresponding to fig. 6, 

 showing the openings of the right and left livers into the stoma<?h. 



