287 



consist of stronger forms than those inhabiting the regions 

 that abut upon it, so that the faculty of extending their range 

 is possessed in a greater degree (PI. IX, lig. 7). 



He also recognises that the ancestral bird life of America, 

 which at the present day is chiefly confined to South America, 

 once occupied the whole Western Hemisphere, but by competition 

 have now a very limited range. 



In North America, the IMissourian or Central Desert region 

 is equally regarded as a sanctuary or refuge of archaic bird 

 life by Prof. Newton, who records that here is found the most 

 undifferentiated and generalised form of American ornithic 

 life, so that it may be considered as the " focus" of Nearctic 

 types. 



In Entomology little, comparatively, has been done in this 

 direction of philosophical inquiry, and our knowledge of the 

 internal structure of insects is so limited, and the considered 

 opinions of those who have studied the subject so few and frag- 

 mentary, that material for judgment is very deficient. Never- 

 theless the few facts that can be gleaned of relative generic 

 dominancy are all strongly confirmatory^ of the truth of the 

 contentions of this thesis. 



In Lepidoptera, although Mr. Meyrick (to whom and to 

 Dr. LoNGSTAFF I am greatly indebted for much valuable in- 

 formation) has by his great knowledge worked out with infinite 

 labour a series of probable phylogenies, based upon the external 

 morphology, yet little beyond this has been done to elucidate 

 the phylogenetic sequence of the different families and genera, 

 either as revealed by their internal structure or as indicated 

 by their geographical distribution. 



Dr. Sharp has, however, declared that the genus Vanessa, 

 a group especially characteristic of the Northern Hemisphere, 

 may be considered the dominant butterflies of the world, and 

 the most capable of prospering under any varied or adverse 

 conditions to which it may be exposed. This genus in its broad 

 sense contains one species, Pyraincis carctui, which is of so 

 adaptable a nature that it is almost world-wide in its range. 



The Nymphalidce, to which Vanessa belongs, he also regards 

 as the predominant family among the butterflies. 



The Micropterygidœ are, according to Meyrick. the primeval 



