POPULATION PROBLEMS 191 



difficult to get our facts clear-cut and complete. A 

 falling stone near the earth's surface has an accelera- 

 tion of about 32 feet per second. That is a clear-cut 

 complete fact. But when we say that nesting terns 

 can find their way home over an unknown area from 

 a distance of a thousand miles, the fact is less ^clear- 

 cut and less complete. Half-a-dozen questions rise at 

 once, what percentage find their way, how long do 

 they take, do they fly in a straight line or tentatively 

 hither and thither, and so on. And when we say 

 that the crude birth-rate in Ireland in 1901 was 22*7 

 per 1,000 of the population, and that of Scotland 29*5, 

 we are stating a fact so incomplete that it is positively 

 misleading. We have to know, for instance, the rela- 

 tive numbers of child-bearing women in that year in 

 the two countries. We have to know how many mar- 

 ried couples emigrated from Ireland in 1901 before 

 their first child was born. The more complex the 

 phenomena, the more difficult is it to get clear-cut 

 complete facts. 



§ 2. Biological Alternatives as regards Population : 



THE Spawning Solution and Economised 



Reproduction 



To understand population problems it is first of all 

 necessary to get the biological foundations clear. Liv- 

 ing creatures are encompassed by difficulties and hmi- 

 tations. To these they answer back in many different 

 ways, using armour, weapons, capacities of con- 

 cealment, circumventions, changes of habit and habitat 



