485 



and correctly reason upon, in terms of forces and motions like 

 those of sensible masses. Polarity is regarded as a resultant of 

 snck forces and motions ; and when, as happens in many cases, 

 light changes the molecular structure of a crystal, and alters its 

 polarity, it does this by impressing, in conformity with mechanical 

 laws, new motions on the constituent molecules. That the reviewer 

 should present the mechanical conception under so extremely limited 

 a form, is the more surprising to me because, at the outset of the 

 very work he reviews, I have, in various passages, based inferences 

 on those immense extensions of it which he ignores ; indicating, for 

 example, the interpretation it yields of the inorganic chemical 

 changes effected by heat, and the organic chemical changes effected 

 by light (Principles of Biology, 13J 



Premising, then, that the ordinary idea of mechanical action must 

 be greatly expanded, let us enter upon the question at issue the 

 sufficiency of the hypothesis that the structure of each organism is 

 determined by the polarities of the special molecules, or physiologi- 

 cal units, peculiar to it as a species, which necessitate tendencies 

 towards special arrangements. My proposition and the reviewer's 

 criticism upon it, will be most conveniently presented if I quote in 

 full a passage of his from which 1 have already extracted some ex- 

 pressions. He says : 



" It will be noticed, however, that Mr. Spencer attributes the possession 

 of these ' tendencies,' or ' proclivities,' to natural inheritance from 

 ancestral organisms ; and it may be argued that he thus saves the 

 mechanist theory and his own consistency at the same time, inasmuch as 

 he derives even the ' tendencies ' themselves ultimately from the environ- 

 ment. To this we reply, that Mr. Spencer, who advocates the nebular 

 hypothesis, cannot evade the admission of an absolute commencement of 

 organic life on the globe, and that the ' formative tendencies,' without 

 which he cannot explain the evolution of a single individual, could not 

 have been inherited by the first organism. Besides, by his virtual denial 

 of spontaneous generation, he denies that the first organism was evolved 

 out of the inorganic world, and thus shuts himself off from the argument 

 (otherwise plausible) that its ' tendencies ' were ultimately derived f roir 

 the environment." 



This assertion is already in great measure disposed of by what 

 has been said above. Holding that, though not " spontaneously 

 generated," those minute portions of protoplasm which first dis- 

 played in the feeblest degree that changeability taken to imply life, 

 were evolved, I am not debarred from the argument that the " ten- 

 dencies " of the physiological units are derived from the inherited 

 effects of environing actions. If the conception of a '-first organ- 

 ism " were a necessary one, the reviewer's objection would be valid. 

 If there were an " absolute commencement " of life, a definite line 

 parting organic matter from the simplest living forms, I should be 

 placed in the predicament he describes. But as the doctrine of 

 Evolution itself tacitly negatives any such distinct separation ; and 

 us the negation is the more confirmed by the facts the more we 



