THE LOCATION OF THE CHICK EMBRYO UPON THE 



BLASTODERM. 



BT 



FLORENCE PEEBLES, Ph.D. 

 With 2 Plates and 15 Figures in the Text. 



An experimental study of the avian egg has led me to examine 

 the following points: 



1. The location of the embryo in the material of the unincubated 

 blastoderm. 



2. The direction of growth before, and after the appearance of 

 the primitive streak. 



3. The origin of the material from which the later embryo 

 arises. 



According to Kopsch^ this third point has been definitely 

 settled. He concludes that nearly all of the embryo develops 

 from the primitive streak. I quote his own words: "Somit 

 entsteht der Embryo, mit Aussnahme des praechordalen Teils, 

 des Kopfes, durch Umwandlung des Primitivstreifens." 



P have already mentioned some experiments, and will describe 

 others, in the following pages, which seem to prove that only the 

 trunk and caudal regions of the embryo arise from the material 

 of the primitive streak. 



The methods used by Assheton, myself, and Kopsch are practi- 

 cally the same, and therefore require little explanation. I have 



^Kopsch, Fr. Ueber die Bedeutung des Primitivstreifens beim Hiihnerembryo. 

 Leipzig, 1902. 



^Peebles, F. A Preliminary Note on the Position of the Primitive Streak, and its 

 Relation to the Embryo of the Chick. Biolog. Bulletin, Vol. IV, No. 4, 1903. 



