448 PRIMARY FACTORS OF ORGANIC EVOLUTION. 



or disproved. I have termed it a "dynamic theory," 

 and it is in some respects similar to that subsequently 

 proposed by Haeckel under the name of the "peri- 

 genesis of the plastidule." I have already referred to 

 the phenomena of the building or growth of the added 

 characters which constitute progressive evolution as 

 evidence of the existence of a peculiar species of en- 

 ergy, which I termed bathmism. This is to be ex- 

 plained as a mode of motion of the molecules of living 

 protoplasm, by which the latter build tissue at par- 

 ticular points, and do not do so at other points. This 

 action is most easily observed in the beginnings of 

 growth, as in the segmentation of the oosperm, the 

 formation of the blastodermic layers, of the gastrula, 

 of the primitive groove, etc. In the meroblastic em- 

 bryo the energy is evidently in excess at one part of 

 the oosperm, and in defect at another. This is a sim- 

 ple example of the "location of growth force or bath- 

 mism." In all folding or invagination there is ex- 

 cess of growth at the region which becomes the con- 

 vex face of the fold; i. e., a location or especial ac- 

 tivity of bathmism at that point. All modifications of 

 form can be thus traced to activity of this energy at 

 particular points. A basis is thus laid for a more or 

 less complex organism, and the channels of nutritive 

 pabulum being once established, the location or dis- 

 tribution of the energy is assured in the directions in 

 which they lead. Thus with the establishment of cir- 

 culating channels nutrition is definitely guided to par- 

 ticular points. It is evident that on this hypothesis 

 the bases of evolutionary change are laid in the em- 

 bryonic tissues, where bathmism displays its activity 

 in producing the base forms on which all subsequent 

 structure is moulded. 



