PARTHENOGENESIS AND ITS SEQUEL 303 



are not of their own seeking, they are inherent mani- 

 festations of variations of growth, uncontrollable save 

 by the machinery of Natural Selection. Incidentally 

 such victims serve a useful purpose, for their myriad hosts 

 afford food for hordes of other animals, which in turn are 

 eaten. Little though we realize it, the well-being of 

 the human race would suffer if these prolific creatures — 

 the uncomplaining victims of that inexorable law which 

 bids all living things " increase and multiply " or die — 

 should cease to be ; for with them would disappear a 

 host of animals on whose existence man's comfort more 

 or less depends. 



During the millions of years that have rolled by since 

 the first appearance of life on the earth, who shall count 

 the number of types which have been exterminated 

 without leaving the faintest trace of their having ever 

 existed ? The survivors which have contrived to main- 

 tain a place in the sun present an infinite range of 

 variation in colour, size, habit, and structure, as well as 

 in emotions. These varied aspects are all so many facets 

 of the mysterious phenomenon we call Life : and they 

 are so many witnesses of the v«rsatility of Life. Not 

 the least mysterious feature of this Life is its faculty 

 of reproduction, which expresses itself in an infinite 

 variety of ways, defying all but the crudest forms of 

 analysis. The evolution of sex has exercised the specu- 

 lative ingenuity of some of the acutest students of 

 Nature from the earliest times, and we are still far from 

 a satisfactory solution of the problems it presents. 

 Hermaphroditism and Parthenogenesis are commonly 

 regarded as degenerate forms of reproduction, but it 

 would probably be more correct to see in them exceptional 

 modes of adaptation enabling such individuals to occupy 



