372 THE WORLD OF LIFE chap. 



they prefer the conception of a universe in which pain exists 

 perpetually and uselessly, to one in which the pain is strictly 

 limited, while its beneficial results are eternal \ 



None of these writers, however, nor, so far as I know, 

 any evolutionist, has ever gone to the root of the problem, 

 by considering the very existence of pain as being one of 

 the essential factors in evolution ; as having been developed 

 in the animal world for a purpose ; as being strictly sub- 

 ordinated to the law of utility ; and therefore never developed 

 beyond what was actually needed for the preservation of life. 

 It is from this point of view that I shall now discuss the 

 question, and it will be found that it leads us to some very 

 important conclusions. In order to do this, we must con- 

 sider what were the conditions of the problem when life first 

 appeared upon the earth. 



The general facts as to the rate of increase of animals 

 and plants have been given in Chapter VII. of this work ; 

 but even these facts, remarkable as they are, seem altogether 

 insignificant when compared with those of the lowest forms 

 of life. The most startling calculation of the kind I have 

 seen was given last year in a Royal Institution lecture on 

 The Physical Basis of Life, by W. B. Hardy, F.R.S. (a 

 Cambridge tutor), as to one of the infusoria (Paramecium) 

 much used for experiment and observation on account of 

 its comparatively large size (about -j-ho mcn l° n g) anc * lis 

 being very easily procured. This species multiplies by 

 division about twice in three days, and has been kept under 

 observation thus multiplying for more than ioo generations. 

 Now it is not very difficult to calculate what quantity of 

 Paramecia would be produced in any given number of 

 generations, and what space they would occupy. No non- . 

 mathematical person can imagine or will believe the result. 

 It is, that if the conditions were such (as regards space, 

 food, etc.) that the Paramecium could go on increasing for 

 350 generations, that is to say, for about two years, the 

 produce would be sufficient in bulk to occupy a sphere 

 larger than the known universe ! 



Now taking this as a type of the Protozoa — the one- 

 celled animals and plants that still exist in thousands of 

 varied forms — we see in imagination the beginnings of the 



