ENVIRONMENTAL FACTORS ^5 



learning them thoroughly in the time at his disposal, he has 

 the satisfaction of being able to solve problems, often of great 

 practical importance, which cannot possibly be solved by having 

 a profound grasp of only one field of science. Many people 

 find it rather a strain if their work includes more than one or 

 two " subjects," and this is probably the reason why many 

 who start doing ecological work end up by specialising on one 

 of the ready-made subjects with which they come in contact 

 in the course of their ecological researches. It is quite true 

 that one is frequently held up by the absence of existing data 

 about some problem in geology or chemistry, and it may be 

 necessary to turn to and try to solve it oneself. It is also true 

 that the division of science into water-tight compartments 

 is to be avoided like the plague. At the same time there are 

 problems in the reactions of animals with their environment 

 which call for a special point of view and a special equipment, 

 and one of the most important of these is a slight knowledge of 

 a number of different subjects, if only a knowledge of whom 

 to ask or where to look up the information that is required. 



3. Suppose one is studying the factors limiting the dis- 

 tribution of animals living in an estuary. One would need to 

 know amongst other things what the tides were (but not the 

 theories as to how and why they occur in a particular way) ; 

 the chemical composition of the water and how to estimate 

 the chloride content (but not the reasons why silver nitrate 

 precipitates sodium chloride) ; how the rainfall at different 

 times of the year affected the muddiness of the water ; some- 

 thing about the physiology of sulphur bacteria which prevent 

 animals from living in certain parts of the estuary ; the names 

 of common plants growing in salt-marshes ; something about 

 the periodicity of droughts (but not the reasons for their 

 occurrence). One would also have to learn how to talk 

 politely to a fisherman or to the man who catches prawns, 

 how to stalk a bird with field-glasses, and possibly how to 

 drive a car or sail a boat. Knowing all these things, and a 

 great deal more, the main part of one's work would still be 

 the observation and collection of animals with a view to 

 finding out their distribution and habits. Having obtained 



