THE SPECIFIC CHARACTERISTICS OF VITALITY 551 



Homogeneous non-living matter makes no spontaneous 

 efforts from within towards heterogeneity. 



If any one cares to regard the breaking off of a portion of 

 a crystal as analogous to the giving birth to an immature 

 organism, capable, in due time, of an independent existence, 

 he may do so as a poetical exercise, but not as any contribution 

 to the philosophy of biology. 



The power of sexual reproduction is entirely sui generis, 

 and has no analogy in the non-living world. The so-called 

 similarities between sexual phenomena and the attraction of 

 oppositely electrified atoms or ions are really only pretty 

 fancies. Possibly the most mysterious or wonder-rousing 

 property of living matter is its inherent power of progressive 

 cell-differentiation . 



Out of the single fertilized ovum (or egg), usually of micro- 

 scopic size, there arises in due time the perfect animal ; the 

 simple ovum having given place to millions of cells, each 

 having its own niche in the living mosaic. And the end-pro- 

 duct of the cell evolution is highly characteristic, for the 

 microscopist can tell at a glance a brain-cell from a liver- 

 cell, a bone-cell from a cell of the retina, and so on. 

 Morphological differentiation evidently underlies functional 

 specialisation. 



Sometimes these self-developing systems are spoken of as 

 " mechanisms," but that is justified only in the interests of 

 brevity of expression : no man-made mechanism ever evolved 

 itself, or, being made, ever became anything else ; but this is 

 precisely what the " mechanisms " of protoplasm are con- 

 tinually doing. The single and simple can evolve into the 

 multiform and complicated merely, apparently, by possessing 

 the power of assimilation. The like can evolve into the unlike ; 

 the cells of the embryo which at one stage are practically all 

 alike are destined to become something exceedingly different, 

 as different as brain from bone. A mere mass of spherules 

 will shortly become all the complexities of the eye or ear ; 

 some lens cells detached from the lens of the eye can produce 

 a lens outside of and away from the eye altogether ; some 

 bone cells placed on the skin forthwith proceed to develop 

 bone on the outside of the body. 



It is customary to make a great deal out of radium being 

 able to disintegrate and become something else as though 



