38 BIOLOGICAL LECTURES. 



mechanisms, each with precisely the same type of potentiality 

 as that of the whole o.^^. (See concluding note.) 



There may, according to the foregoing view, be such a thing 

 as perfect isotropy in every radius lying in a plane cutting the 

 line from a to d at right angles. This would not, however, 

 be the perfect isotropy of our definition, that we are com- 

 pelled to accept in the form in which it comes to us from the 

 physicist. 



As development proceeds, moreover, we have reason to be- 

 lieve that this aeolotropy becomes more and more marked, so 

 that eventually the huge metameric molecules become ar- 

 ranged in definite linear, parallel systems, as in the axis cylin- 

 ders of nerve cells and in muscular tissue. Here the charac- 

 teristics of the system become the same in parallel lines, and 

 in any directions at right angles to an axis parallel to these 

 parallel lines of molecules. That is, in certain rectangular 

 directions there is an approximation toward homogeneity. But 

 the completest homogeneity is found to occur in only one 

 direction in parallel lines extending through the mass. This 

 condition we may designate as monotropy. Starting with the 

 extreme aeolotropic condition of the germ we must, therefore, 

 assume that as organization becomes more and more complete, 

 in the progress of development, in the specialized systems of 

 tissues and organs, the molecules become more and more defi- 

 nitely monotropic. Therefore they at last become incapable, 

 as dynamical systems, of exhibiting a complex development 

 such as is manifested by a germ, but capable only of manifest- 

 ing the special physiological functions entailed by their dynam- 

 ically and mechanically evolved monotropism. 



We can now understand why it is that the germinal matter 

 of a species always remains in an aeolotropic state. Since 

 germinal matter is always relieved of specialized functions in 

 the body of the parent, it must perforce remain in its primitive 

 condition of germinal potentiality as a molecular mechanism. 

 Since the germ is material that has been produced in excess of 

 the needs of metabolism of the parent body, as supposed by 

 Haeckel and Spencer, it can do no work for that body. The 

 unbroken continuity of the processes of metabolism have pro- 



