48 



EARLY EMBRYOLOGY OF THE CHICK 



In 24-hour embryos the intermediate mesoderm shows very 

 little differentiation. In the [chick it never becomes segmen tally 

 divided as does the dorsal mesoderm. The fact that it is 

 potentially segmental in character is indicated, however, by 

 the way in which it later gives rise to segmentally arranged 



— proamnion 

 region 



Fig. 17. — Diagrams of sections of 24-hour chick. The sections are located 

 on an outline sketch of the entire embryo. The conventional representation of 

 the germ layers is the same as that employed in Fig. 13 except that here where 

 its cells have become aggregated to form definite layers the mesoderm is repre- 

 sented by heavy solid black lines. 



nephric tubules. Because of the part it plays in the estabhsh- 

 ment of the excretory system the intermediate mesoderm is 

 frequently called the nephrotomic plate. 



