SIGHT — FIELDWORK AND EXPERIMENTS 3I 



These older, but beautifully made examples of the optical 

 worker's art can still be bought second-hand ; and provided 

 that the objectives, eye-pieces and condensers have lenses 

 free from scratches, and the working parts are not too slack, 

 they will be capable of many more years of use. They may 

 often be bought at a reasonable price, but if the student is 

 not fairly well acquainted with microscopes the help of a 

 knowledgeable friend when buying the instrument will save 

 pounds in repairs and adjustments. 



It is hardly necessary to add that such an aid as a micro- 

 scope will not be limited to studying the visual organs of 

 small animals ; it can be equally useful for the examination of 

 sensory hairs, insects' antennae and limbs, and other objects. 



Now, it is often said by some authorities that observations 

 carried out on captive creatures in aquaria, vivaria, cages 

 and so on do not give accurate indications of an animal's 

 true behaviour. After many years of experience, I do not 

 accept this as wholly true. Most animals will display many 

 of their basic activities under captive conditions so long as 

 their requirements as to space, dryness or dampness, ventila- 

 tion and temperature are provided. This means that the 

 student can, with much advantage, keep many kinds of 

 animals under constant observation. However, the captive 

 specimen will not provide all the information desired, and 

 nothing quite takes the place of fieldwork. A combination 

 of field observations and captive creatures will give the best 

 possible results. 



I should like to recall a number of personal experiences 

 in the field, and with animals which I have kept, because 

 I think these accounts may be of value. They may also serve 

 to stimulate those who are interested in the senses of animals 

 to see for themselves and to learn that observations in the 

 laboratory, the animal house or room, and in the wild, will 

 provide the wide range of study necessary if a sense of pro- 

 portion and a complete picture is to be acquired. It will be 

 obvious that only a few examples in each group of animals 

 will be possible in a single volume ; but the accounts I shall 

 give have been carefully chosen so as to present some prac- 

 tical instances of the operation and use of the sensory abilities 

 of the creatures dealt with. 



