268 LILLIE. [Vol. XVII. 



If the basis of these adaptive cleavage forms is cytoplasmic, 

 as I believe, the complexity of the cytoplasmic organization 

 must be great. The preceding examples illustrate this. But 

 no phenomena of this sort give so overwhelming a sense of 

 the inadequacy of our theories of development as the fact that 

 cleavage may actually exhibit ancestral reminiscence (Wilson, 

 '98). Admitting that reminiscence of ancestral conditions is 

 ever shown in ontogeny, no one who is conversant with the 

 literature of cell lineage can doubt that Dr. Wilson has placed 

 the phenomena which he describes in their natural category ; 

 they belong to the same order of events as the development of 

 tooth germs in a whale embryo. No one who has become con- 

 vinced that true homologies are found in cleavage, and that the 

 cleavage may exhibit adaptive modification, can be surprised by 

 this last discovery. But these phenomena bring us so near 

 to the unsegmented Q.%g, that the conclusion is unavoidable 

 that homology, adaptation, and ancestral reminiscence have a 

 protoplasmic basis, and are not merely dependent on the recur- 

 rence of similar conditions. 



Another conclusion that follows directly from this is that 

 the Q.g% transmits far more than the spermatozoon, at least in 

 these early stages. All those features of the early develop- 

 ment that are dependent on the organization of the cytoplasm 

 must be transmitted by the ^gg alone. Driesch ('98) has gone 

 to work in the right way with his experiments on hybridization, 

 to determine what features of the early development are purely 

 maternal in their origin. Before his experiments were pub- 

 lished I had begun some similar experiments on fish-eggs to 

 determine the influence of hybridization on the cleavage ; but 

 reached no certain results, owing to difficulties offered by the 

 material. Experiments of this sort on eggs exhibiting deter- 

 minate cleavage are much to be desired. The annelids would 

 offer, perhaps, the best opportunities for this kind of work. 



Coordinated and definitely directed forces imply a mechanism 

 of definite configuration ; what idea can we form of the config- 

 uration of this mechanism.^ In the first place, it should be 

 observed that, inasmuch as the capacity for typical develop- 

 ment is not dependent on the maintenance of the integrity of 



