Hyhridizalion of EcJiiituiilii. 41 



9. The facts suggest an emission of enzymes rather than an emis- 

 sion of chromatin. 



10. The results show that in the cross-activated Cidaris eggs an 

 orderly series of developmental reactions is disorganized by the foreign 

 nuclear material at the time when divergence of two systems of 

 development occurs. 



11. Through its organization and in its capacity as substrate the 

 egg fixes the course of development. 



CONCLUSIONS. 



The consideration of the facts established during the stud}'' of the 

 material which has formed the basis of this paper gives a deep impres- 

 sion of the fundamental fact of organization. It gives additional 

 proof of the existence of an underlying basis for development, which 

 we may be able to distort, but which we are not yet able to shape 

 at will. 



The normal development of the Cidaris egg is of a less-specialized 

 type than that of the eggs of the species whose sperms were used in 

 the cross-activations. As long as the two courses of development 

 lie parallel, we say that development is normal. When the point of 

 divergence between the two paths is reached, characters appear 

 which we call aberrant. Differentiation lies in a series of reactions 

 between nucleus and cytoplasm. In attempting to superimpose a 

 specialized on a non-speciahzed type of development we fail, because 

 of our lack of ability to harmonize two disharmonious systems of 

 development. 



The consideration of this material emphasizes again the fact that 

 the thing inherited by offspring from parent is the capacity for 

 development. What that development will be depends on the 

 interactions between nucleus and cytoplasm and on adjustment to 

 environment. The cytoplasm is the material that is shaped during 

 the series of reactions. It is because of the fact that the cytoplasm 

 of the egg is the material basis of the body that Conklin's statement 

 that the egg cytoplasm ''fixes the general type of development" 

 is true. 



