72 The Unity of the Organism 



this remark go even in a tentative discussion of this vastly 

 important subject. If it is merely a question of equality 

 of claim upon belief as between the two conceptions so far 

 as logic is concerned, what is to determine the choice? Why 

 not accept the elemental as well as the organismal way of 

 interpreting the case if logically its claims be equal to that 

 of the latter? Because, I answer with emphasis, the observa- 

 tional evidence is stronger in favor of the organismal inter- 

 pretation. That is the sole legitimate ground on which to 

 rest the decision. Assuming, as we do, that Weismann and 

 Goette are equally competent and trustworthy investigators, 

 and basing the decision for the present on their results alone, 

 we are bound to recognize that Goette has brought forAvard 

 much more observational evidence that the migration of the 

 sex-cells is largely though not wholly passive than Weis- 

 mann has that it is wholly active. 



Remarks on the Relation of Germ-Cells to Germ-Layers and 



to the Organism Generally 



Before taking leave of the concrete objects, germ-layers 

 and germ-cells, I speak of one aspect of the general results 

 of our examination which may escape the reader unless his 

 attention is specially directed to the matter. In all those 

 animals in which the sex-cells do not appear until the lay- 

 ered stage of the embryo is reached, and in which these cells 

 arise by a genuine transformation of cells of the layer, as 

 they do in hydromedusse, the layers are gemiinal in a very 

 fundamental sense, for it is in them that the transformations 

 begin which issue in the completed tissues and organs of all 

 sorts, the sexual tissues and organs with the rest. Viewed in 

 this light the germ-layers have, on the whole, gained rather 

 than lost in importance and interest, for while we are led 

 to deny the rigorous specificity to each particular layer as 

 to what may or may not arise from it that often constituted 



