122 DEVELOPMENT OF THE FROG'S EGG [Cn. XI 



non-injured side, whole embryos of half-size, but he believes 

 that at first there formed a half -gas trula, then a half-embryo. 

 Later this half -embryo completed itself without using material 

 from the injured side! That is to say, by using "wandering 

 cells " the half-embryo has postgenerated the other half of its 

 body ! 



