22 



significant ; let us advert to a few of the more prominent 

 cases in which our instinct would seem to warrant the 

 belief that aberrations are to be usually anticipated. 

 And since it will hardly be denied that, like the repre- 

 sentatives of other departments of the animate world, 

 insects may, in their outward configuration and deve- 

 lopment, be in some measure under the control of the 

 external influences to which they are immediately ex- 

 posed, we will take a rapid glance at a few of the circum- 

 stances and conditions which are known to have more or 

 less of a qualifying effect on the members of large and 

 opposite sections of the organic creation ; and then see 

 how far we are enabled, by means of facts, to trace out 

 results for the Insecta, corresponding to those which are 

 admitted to obtain in the other groups. And, since the 

 existence of analogous results infers, to a certain extent, 

 the similarity of the agents which have brought them 

 about, our " causes of variation ' (provided the effects 

 can be shown) may be in reality almost demonstrated. 



Amongst the numerous influences and conditions, in 

 obedience to which the members of a large proportion 

 of the animate world would appear, at times, in their 

 outward aspect to be modified or fashioned, the following 

 may be selected as perhaps of primary importance : 



1. Climatal causes generally (whether dependent on 

 latitude or upon altitude). 



2. Temporary heat or cold, of an unusual degree. 



3. Nature of the country and of the soil. 



4. Isolation, and exposure to a stormy atmosphere. 



