520 THE CHANGING WORLD 



Struggle for Existence 



As a consequence of the prodigality of overproduction, there follows 

 a struggle for existence, which is simply the result of an effort on the 

 part of every creature to live and leave descendants. This struggle 

 may be against environmental conditions, between individuals of the 

 same species, or between individuals of different species. 



Bumpus describes a case of the first sort in which some sixty 

 English sparrows out of a colony wintering in a church belfry 

 perished in a sleet storm. When they were statistically compared 

 with an equal number of survivors with respect to ten measurable 

 anatomical features, it was found that those which perished in the 

 struggle for existence under the adverse environment of the sleet 

 storm were the most variable ones at either extreme, that is, the 

 anatomical geniuses and dullards, while the conservative average 

 ones survived. 



An example of the second kind of struggle for existence is found in 

 the competition between a parent plant and its offspring for moisture, 

 standing room, air, light, and nutriment. Most plants have well- 

 known devices for lessening this competition by scattering their seeds 

 outside the immediate parental environment. Among animals, as 

 also even among humans, there are all sorts of inducements to make- 

 the young shift for themselves and not to continue to live off their 

 parents. 



The cobweb house-spider, Theridium, hangs up a little pear-shaped 

 woven bag with several dozen tiny eggs in it. When these hatch out 

 within the bag, there is nothing for the young spiders to eat except 

 brothers and sisters, which they proceed to devour. The first ones to 

 hatch have a decided advantage, and finally, only two or three of the 

 whole lot triumphantly emerge out of the woven bag. The worse 

 a spider is ethically, according to human standards, the better that 

 spider is as a spider. It is thus seen that not only the movements 

 of the heavenly bodies are subject to Einstein's law of relativity, but 

 that ethics are also. 



There is finally an age-long struggle also between carnivores and 

 their prey, and between different organisms of all sorts for food, and 

 for whatever else is necessary for the maintenance of life. It is not 

 all competition, however, since co-operation frequently enters into the 

 struggle for existence, as is instanced by the mutual protection secured 

 in flocks and herds. This gives an altruistic touch to the picture. 



