Plate XVII. 



[The magnification is the same for all figures: Cx2, with the single 

 exception of fig. 4 which is Ex 2.] 



a.pn.1-6, Anlagen of ])ronephric 

 tubules from the first to sixth. 

 a.sd., Anlage of segmental duct. 

 ed., collecting duct. 

 cli., chorda doi'sali.s. 

 cut., cutis-layer of myotome. 

 d., dorsal row of mesohlast. 

 cp., epiblast. 

 Idj., hypoblast. 

 l.m.^ lateral [)late of mesoblast. 



m., median row of mesoblast. 

 m.jj., parietal layer of mesoblast. 

 mes., mesoblast. 



mt.I, II, &c., the first, second, &c. 

 myotome. 



mus., muscle-layer of myotome. 

 m.v., visceral layer of mesoblast. 

 n., neural cord or canal. 

 v., ventral row of mesoblast. 



Fig. 1. A transverse section through the dorsal region of an embryo inter- 

 mediate between ytaü;es i and ii. 



Fig. 2-7. From a series of transverse sections through a younger embryo 

 of Stage 11. 



Figs. 8-17. From a series of transverse sections through an older embryo 

 of fcîtage II. 



Figs. 18 ar.d 19. Two sections from a series of cross-sections through a little 

 more advanced embryo than the last. 



Figs. 20-29. From serial cross-sections througli the most advanced embryo 

 of »Stage 11. 



