THE BIOLOGY OF THE CELL SURFACE 



2. This same conclusion holds for the data on merogony. 

 It may be regarded as proved that all eggs which can be 

 fragmented before fertilization have the capacity for the 

 production of many embryos. Merogonic development 

 Indicates strongly, especially in determinate eggs, that 

 dliTerentlation ensues as a restrictive process — restricting 

 potency for multiple embryo-formation to one. The theory 

 of segregation In these cases would imply telescoping of 

 several embryos. 



3. Some fragments of eggs contain the egg-nucleus and 

 hence when fertilized develop with two nuclei constituting 

 a diploid nucleus. In such fragments restriction obtains 

 as in whole eggs, except that the chromosomes remove less 

 cytoplasmic stuff since less is available. From the point 

 of view of embryonic segregation, we would have to assume 

 that since perfect though dwarfed embryos result from the 

 fragments, the segregates in whole eggs are pluralistic. 

 From this it should follow that all eggs when separated Into 

 blastomeres should develop into entire organisms or Into 

 embryonic regions, each containing parts reduplicated. 



4. The development of blastomeres Isolated during 

 cleavage Into perfect though dwarf embryos stands as 

 strong evidence that restriction and not segregation under- 

 lies differentiation. For how from already segregated 

 areas could perfect embryos arise .^ Or, if it be postulated 

 that the areas are not yet segregated at the stage of Isola- 

 tion, why do the blastomeres in an Intact egg not develop 

 each into an embryo.^ On the basis of our theory of 

 restriction, potencies bound in the cytoplasm In the Intact 

 Qgg become free in the Isolated blastomeres because of the 

 new conditions set up by Isolation. 



5. If we put forward the theory of segregation to account 

 for the diiTerentlation occurring In a parthenogenetic egg 

 containing a nucleus with half the number of chromosomes 

 found In the eggs of this species when they are fertilized, 



3iS 



