16 



task of mechanical compilation. I am bound to admit that I 

 did it execrably, and the recollection is painful to me. I have 

 repented for many years, and think that I can promise never 

 again to offend in the same way. 



But the young naturalist, in particular, eager for promising 

 openings, in order that he too may be of use, and bring forth 

 his faculties into the light of day (a most praiseworthy ambition !) 

 will ask for more definite instructions. " If we are not to do 

 what we see our neighbours on every hand doing with all their 

 might, what are we to attempt ? " 



I think that the young naturalist can hardly go wrong if he 

 takes seriously to heart this one maxim : that he is to study 

 plants and animals as living things. If he studies structure, let 

 him incessantly recall that these tissues and parts are the organs 

 of a living animal or a living plant. How are they meant to 

 act — why are they found in this organism and not in that ? If 

 he collects, let him try to find out why a particular aquatic in- 

 sect, for example, is found in this stream and not in the next. 

 Lists will not help him, he must bend his mind to the problem, 

 and consider all the circumstances — ^presence or absence of 

 food, of known enemies, and so on, and the causes of these in 

 their turn. He need have no fear that the field is too well ex- 

 plored beforehand. Having been led, more or less accidentally, 

 to interest myself of late years in aquatic insects, I find that 

 their life-histories and their adaptations to environment have 

 been, with rare exceptions, altogether neglected. We make a 

 good beginning in Swammerdam ; Reaumur succeeds, and even 

 improves upon his predecessor ; De Geer makes a good third. 

 Then we come to the writers of little monographs and studies 

 — deficient perhaps in grasp and fertility, but interesting and 

 useful. A scattered and broken succession of these carries us 

 down to the present day, leaving us with this result, that the 

 structure and mode of life of the vast majority of common insects 

 have never yet been investigated at all. 



I suspect that the same holds true of other branches of 

 Natural History also. Take any common aquatic plant, for 

 instance, and ask why its leaves are of this particular shape. 

 How does it face such and such an emergency ? How is it dis- 

 persed ? If you put these obvious questions, no one can answer. 

 I have found it easy to make new observations on Duckweed, 

 one of the most plentiful of green plants, and it would be the 



