16 Variatio}is in the Animal Kingdom. 



come to consider the causes which produce variation, viz., 

 geological, proximity or distance from the sea, temperature, 

 rainfall, and excess or absence of bright sunshine, it is not 

 difficult to imagine that species are the fixed points or resting 

 places of such variation ; as such species begin to adjust them- 

 selves to their new conditions as soon as these conditions begin 

 to change or become abnormal. 



These few observations naturally lead up to a few words, in 

 closing, upon the basis upon which zoological collections should 

 be formed, so as to be of real use in helping us to understand 

 the subjects to which they refer better than we do at present. 

 Nearly all collections are made upon the basis of systematic 

 classification, from which it follows that one good collection of, 

 say British, Lepidoptera is very like another, and so on. All the 

 well-known ground is gone over, over and over again, and if a 

 collection happens to attain to the proud distinction of being 

 considered better than another, it is probably because it contains 

 a longer row of one or two recognised good things, or a few 

 abnormal forms, perhaps cripples, monstrosities, or herma- 

 phrodites. 



Suppose, however, in the case of insects, a collection is 

 devoted to one genus — say, the Pieridae, or white butterflies — 

 and that representatives of this genus be obtained from all parts 

 of the world where it occurs, and from all varying physical 

 localities, might it not be possible to obtain in time such a 

 collection as would render it difficult to say that there was such 

 a thing as species at all ? Even if circumstances rendered it 

 necessary to confine such a collection to the British Islands, it 

 would be of great interest to see large series of common insects 

 from every possible sort of locality, or collected under various 

 conditions of the seasons. 



Then there is the rearing of specimens under artificial or 

 abnormal conditions, by which means variations can be pro- 

 duced ; such specimens, with record of the circumstances by 

 which they were obtained, would also be of great interest and 

 scientific value. 



As I have already stated, it is those species most abundantly 

 met with where we may expect to meet with variation, and it is 

 only in large series, widely collected and carefully arranged, 

 that we may be able to trace out such local variation, and 

 there is no difficulty whatever in collecting in this manner. 

 There seems to be no question that collections illustrating and 

 thoroughly working out one group, family, or genus must be in 

 every way more valuable, more instructive, and more interesting 

 than mere typical collections which show nothing but what has 

 been seen before. 



