656 Organic Physics. [August, 



as a rule— but that direct steps from species to species have been 



Nor is such a method of evolution inexplicable. In fact, Dar- 

 win has, perhaps, unnecessarily limited the application of his own 

 principles, in confining the molding influences to minute varia- 

 tions. We know that there are many variations which are far 

 from being minute. Extreme variations are occasionally pro- 

 duced, and marked variations which are capable of hereditary 



The minute variations considered in the Darwinian theory are 

 of universal occurrence. Perhaps no case ever arises of a com- 

 pletely normal birth — of an offspring precisely intermediate in all 

 respects between its parents. Variations in size and vigor of the 

 body as a whole, of the separate organs of the body, of the tis- 

 sues composing these organs, &c, never fail to occur. There is 

 a constant tendency to deviate from the type. And this tendency 

 is in continual conflict with the opposite tendency produced by 

 the struggle for existence and the necessity of preserving the best 

 adaptation to natural conditions. 



These minor variations may be due to variations in polar vigor 

 of the molecules. We have already considered the question of 

 molecular energy, and ascribed it to the degree of chemical 

 polarity. The most vigorously acid or basic molecules must have 

 the most vigorous growth energy. But this chemical polarity is 

 constantly affected by cell division. The cells arising from con- 

 tinued division of a primary cell must differ widely in polarity, 

 ranging from the neutral to the extreme of acid or basic condi- 

 tions. Perhaps the free buds of the tissue cells may be their 

 most vigorously polar offspring, yet differences cannot but occur 

 in their degree of polarity, and the germinal cell into which they 

 aggregate is perhaps made up of molecules considerably differing 

 in chemical activity. In its evolution the growth vigor of the new 

 tissues must be controlled by the chemical energy of the mole- 

 cules from which they arise. Hence there may be variations from 

 the parental form in every tissue and organ of the new form. The 

 union of germs of two individuals adds a new element of com- 

 plication to the case. If the molecules of the bisexual germs 

 constitute poles of a galvanic circuit, there may be as many 

 diverse circuits as there are diverse sets of molecules, and the 

 chemical energy of each circuit will be controlled by the 



