CHAPTER XIII 



REPRODUCTION 



GROWTH AND REPRODUCTION— SPORES— VEGETATIVE RE- 

 PRODUCTION—SEXUAL REPRODUCTION— ALTERNATION OF 

 GENERATIONS— NUMBER OF OFFSPRING— ORIGIN OF LIFE 

 FROM THE SEA— THE EGG— ANTHEROZOIDS AND SPERMA- 

 TOZOA — HERMAPHRODITISM — PARTHENOGENESIS — OLD 



AGE AND DEATH 



Because, in point of fact, one does see, in this world — which 

 is remarkable for devilish strange arrangements, and for 

 being decidedly the most unintelligible thing within a man's 

 experience — very odd conjunctions. 



Cousin Feenix. Dombey and Son. Chaeles Dickens, 



Growth and Reproduction 



CJne of the distinctions between living organisms and in- 

 organic matter is that the former grow and reproduce and 

 the latter does not. 



It is quite true that crystals and other inorganic substances 

 get larger. But in their case the growth is due to new matter 

 being deposited outside them. Like Mr Weller, senior, when 

 he put on one overcoat after another, they increase in bulk 

 by a series of external accretions. But living organisms take 

 up food and, after digesting it, pass it all through their sub- 

 stance, and it accumulates throughout the body, adding to 

 the existing protoplasm or cell-tissues. This manner of 

 growth is termed intussusception. 



There is, of course, a limit to gro^vth. Trees and elephants 

 are very much bigger than mushrooms and mice. In animals, 

 as a general rule, reproduction occurs at the time that the 

 limit of growth has been reached, though there are many 

 exceptions to this statement ; but many plants grow through- 

 out life and reproduce most of the time. Unicellular plants 

 and animals are often more or less spherical. It is well known 

 that the surface of a sphere increases as the square of the 

 radius, whilst its volume increases as the cube of the radius. 



