Figs. 8 to 11 and 15 to 20, camera-lucida drawings of chick embryos, showing 

 successive stages of development, the so-called primary neuromeres and the 

 neuromeres of later stages. 



Figs. 8 and 9 Embryos of three somites, dorsal view, drawn from living 

 specimens, showing the early beaded appearance of the neural crests. 



Figs. 10 and 11 Embryos of eight and thirteen somites, respectively, dorsal 

 view, drawn from living specimens, showing the brain vesicles and later 

 neuromeres. 



348 



