THE NUMBERS OF ANIMALS 107 



with animals. A little over a thousand animals were brought 

 over in the period from 1891 to the present day, and the 

 multiplication of these, under semi-wild conditions, has resulted 

 in a great increase. It was estimated that there were 200,000 

 of them in 1922.*^ It seems, then, that man is beginning to 

 rectify some of his earlier errors in destroying large and 

 interesting animals, and that the future will in certain regions 

 show some approach to the original condition of things before 

 man began to become over-civilised. 



9. When we turn to the smaller animals such as insects, 

 worms, etc., we find that there are not very many accurate 

 data about the density of their numbers, but it may be safely 

 said that the numbers of most species are immensely great, 

 reaching figures which convey little meaning to most people. 

 Censuses which have been taken of the soil fauna at the Rotham- 

 sted Experimental Station give some idea of the density of 

 numbers reached. ^^* In an acre of arable land there were 

 estimated to be over 800,000 earthworms (these figures being 

 obtained by taking a series of small samples, making complete 

 counts, and then estimating the total number in an acre). In 

 a similar plot of arable land there were nearly three million 

 hymenoptera, one and a half million flies, and two and a 

 third million sp ringtails. These census figures bring out 

 the interesting fact that many groups of small animals which 

 are usually ignored or unfamiliar to zoologists bulk larger 

 in numbers than other groups which have received a very 

 great deal of attention. Such groups are the springtails, of 

 which there were about two and a third millions, while of 

 lepidoptera there were only thirty thousand individuals. 



10. We have attempted to give some idea of the great num- 

 bers of many large animals in the past ; they are still to be found 

 at the present day in secluded parts of the earth. By thinking 

 in terms of large, interesting, and even spectacular species, 

 it is possible to accustom the mind to dealing with the vast 

 numbers in which the smaller, less noticeable, but none the 

 less important forms are nearly everywhere found. We may 

 also look at the matter from another point of view. We can 

 consider what would happen if any one species were allowed 



