A DYNAMICAL HYPOTHESIS OF INHERITANCE. 4 1 



ever that may be arbitrarily chosen, so as to realize the con- 

 tinuance by growth of the same morphological result as that 

 which characterized them normally. These experiments would 

 at first thought seem to prove that some organisms were iso- 

 tropic, but such a conclusion is exceedingly doubtful. It may 

 be that such organisms are, as molecular mechanisms, when 

 subjected to new geotropic and heliotropic conditions, capable 

 of correspondingly new adjustments of their molecular mechan- 

 ical structure. But this would not be proof of isotropy ; only 

 proof of the assumption of a new condition of aeolotropy, 

 adjusted in respect to a new axis of reference, that also coin- 

 cides with some part of the earth's radius prolonged into space. 

 This readjustment of the molecular mechanism may be effected 

 in some way by gravity, as Loeb himself has suspected. It is 

 certainly not due to the control of any lurking "biophors," 

 since it is a purely mechanical readjustment of an ultramicro- 

 scopic structure to new conditions which cannot be effected in 

 any other than a mechanical way. 



The production of monstrosities also may be explained by a 

 dynamical hypothesis, provided we assume that the forces of 

 ontogeny must operate against the statical equilibrium of the 

 parts of the germ at every step. Especially if we assume in 

 addition, as is borne out by facts, that the aeolotropy and con- 

 sequent recapitulative power of the germinal substance is most 

 marked in certain regions of the embryo. These regions, if 

 their molecular equilibrium be mechanically or otherwise dis- 

 turbed by division during development, will assert their germi- 

 nal potentiality and produce an embryo, the relations of which 

 to that already formed alongside of it will be modified by the 

 statical conditions of surface-tension afforded by the adjacent 

 embryo, or the underlying yolk, or by both combined. This is 

 beautifully illustrated by a host of facts. Double toes must 

 have so arisen, as is proved by the direct experiments of Bar- 

 furth, some of which I have repeated, as well as by what 

 happens when the toes of an Axolotl are persistently nibbled 

 off by another animal, when duplication may not only take 

 place in the horizontal plane of the foot or hand but also in 

 the vertical one. In this way a number of supernumerary toes 



