54 THE REALM OF ORGANISMS CONTRASTED 



remarks of Linnaeus that three flies will consume the cap- 

 case of a horse as quickly as a lion can. Professor Woodruff 

 observed the successive asexual generations of the common 

 slipper-animalcule (Paramecium) for five years between 1907 

 and 1912 and found that there were 3,029 of them over 

 three every forty-eight hours. Careful calculation showed 

 that they had given evidence of the capacity of producing in 

 the five years a volume of protoplasm approximately equal 

 to 10,000 times the volume of the earth. This power of 

 self-increase must be taken account of in our conception of 

 living organisms, and the resulting abundance of life must 

 form part of our impressionist picture of Animal Nature. 

 At the autumnal climax of productivity in lakes, there may 

 be to the square yard 7,000 millions of a well-known Dia- 

 tom, Melosira varians, so that the water is like a living 

 soup. 



We have to remember, moreover, the obvious but notable 

 fact that we are dealing not with items like grains of sand, 

 but with individuals, each itself and no other. Mendel put 

 an end to the phrase " as like as two peas ". 



Individual organisms differ greatly in degree of complex- 

 ity and of integration. Many an Infusorian has an intri- 

 cate organisation and lives a by no means monotonous life, 

 though it is only what we somewhat fallaciously call " a single 

 cell ". Hardly any larger than some Infusorians are some of 

 the Rotifers, sometimes with about 1,000 cells; a minnow 

 has its millions, and a bird its millions of millions. What 

 a contrast between the very incipient integration of a 

 sponge, the intricate division of labour in a ' Portuguese Man 

 of War ' hesitating between colony and individual, and the 

 compact co-ordination of the circumspect wren. As a recent 

 student of the subject, Mr. Julian S. Huxley (1912), puts 



