196 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG 



mistakes: it must be that the m.istakes they make are too small to 

 miatter, and have been impotent to alter seriously what is probably a 

 shape of curve characteristic of the phenomenon. 



Trends 



A considerable amount of time was spent in investigating trends, 

 but no evidence of any disturbance to the conclusions was found. One 

 of particular interest concerned the possible effect on spawning of the 

 changes in agriculture due to the war in 1939. Ditches were cleared, 

 and an agricultural revolution took place that might well have affected 

 animals on the farms. There was no significant effect whatever. 



The Variety of Techniques 



Elton (1927) in his pioneer book on ecology has mentioned the 

 need for an ecologist to use the techniques of a number of branches of 

 science. Ecology may, in fact, require almost any branch of knowledge, 

 and is no subject for a person who is not prepared to learn new techni- 

 ques as often as is necessary. It is unreasonable to expect much help 

 from others. Every scientist has his own work to do, and it is only by 

 a lucky chance that one may be found who is willing to collaborate, 

 unless both are working in the same organization, where a co- 

 ordinated approach is natural. Advice that does not take much time is 

 usually freely given, but, in spite of frequent complaints that scientific 

 education is too narrow, there are surely few scientists who cannot 

 teach themselves most of what they need from books and by practice. 

 There is a great difference between the range of chemical knowledge 

 required by a chemist, and the hmited chemical techniques needed, 

 for example, to analyse water for calcium. In industry, junior tech- 

 nicians carry out intricate analyses accurately, but they cannot usually 

 originate methods. I have had no formal botanical training, but from 

 books written by botanists I have learnt to recognize under the micro- 

 scope many of the common algal genera at least. 



Choice of Subject 



Tliis must always be personal, because unless interest is there, success 

 is unlikely, and there is no subject that interests like the one we find 

 for ourselves. The gaps in this book may suggest suitable subjects to 

 anyone, but many of the methods used could be applied to other 

 animals, and of these, there is an unhmited number. It is not necessary 



