32 



thia Cardui, Linn.), the first and second of which occur 

 throughout Europe, in Siberia, Syria, Egypt, Barbary, 

 Nepaul, and Cashmere ; whilst the third (so general in 

 our own country) has been recorded from India, North 

 America, the Brazils, Africa, Java, and New South Wales, 

 however irregular they may be, afford no indications'* 

 of undoubted geographical instability. 



We need not however multiply examples, since our 

 space will scarcely admit of it, and numbers of them will 

 be at once suggested to the entomologist : what it mainly 

 concerns us here to corroborate, is the thesis, that cli- 

 matal operation, although by no means invested with a 

 universal qualifying power, has an amount of influence on 

 certain species, even whilst unconnected with other ele- 

 ments, and therefore, a fortiori, when in combination 

 with them. 



The two principal conditions on which climatal causes 

 generally may be said to rest, are latitude and altitude. 

 As regards the former of these, however, whilst the 

 equatorial and arctic regions of the earth will of course 

 give us the extremes of heat and cold, we shall often 

 perceive differences of temperature (the result perhaps of 

 local circumstances) in areas but slightly removed from 

 each other, sufficient to affect very materially, though 

 by what means it is difficult to understand, the outward 



* Mr. Westwood states that he possesses an individual of the 

 Papilio Machaon from the Himalayan Mountains, captured by Pro- 

 fessor Royle, " which scarcely exhibits the slightest differences 

 when compared with English specimens." The Butterflies of Great 

 Britain, p. 4. 



