PRINCIPLES OF EMBRYOLOGY 



' In UrA. it has not been possible to make any experiments which truly 



11 Ho t&W isolations of gastrula fragments into salt solutions. 



parallel H°l*^ ^' ^, f^'^ ,^^,3 j/^ot contain enough yolk to contmue 



For one thing, the bird tissues oo suDplied with nutrients, 



■■■■i. ^,-;.-"'^. 



Figure 10.7 

 Ontheleftofthe host's.... .ninaucdcnhasW^^^^^ 

 ior half of the same streak used m the ™°7° *°]^^i3 („^ ,he right in the 



eTH*^:tSsvrh?h::n*f("t^^^^^^ 



^ ' I933-) 



solution. Further, the mesoderm and -tod^- J^^^^triS 

 m the eprblast, and it is next door to ^'^'^.'^'^^''^"ItoUion work 

 contahr nothing but V^^-^V^^' ^''T^'^^Z^T^^JO^'^?^^^ -1^" 

 has, however, been carried out, ch-Ay ^Y ^"^^m Id niesoderm (and 

 used fragments of epiblast contammg both ectoderm jj -^ 



often endoderm as well) wHch ^^f f ^^ J^J^t ^as^ularised and 

 membrane of older chick embryos, -^e^ Aey Wn :^^^^^ differentia- 

 continue their histological, though not then nvorph g ^ ^^ 

 tion. The most important result they have obtamed is to snow 



