844 



THE AMERICAN NATURALIST 



[Vol. XL 



abundance in the loose sand on the north coast. The destruction 

 of insectivorous birds, snakes, and Hzards was followed by an in- 

 crease in several injurious insects, particularly ticks, which became 

 a serious pest, and a Coccid moth, the larvae of which bore into 

 the pimento trees." 



Carnivorous Animals Directly Hostile. — The question as to 

 how far the mammals of prey have caused the extinction at various 

 times of various forms of quadruped life is widely disputed. 

 Morris* observes: "So far as existing evidence goes, then, it seems 

 ))robable that hostile aggression, while it may have occasionally 

 been an indirect, has rarely been the direct cause of the extinction 

 of species." The similar opinion expressed to the writer by Dr. 

 L). G. Elliot that no wild animal causes the extinction of another 

 wild animal is probably true (1) of undiminished herds, (2) of 

 cases where carnivores and quadrupeds have evolved together and, 

 as in the case of the modern battleship, modes of defence have 

 evolved simultaneously with modes of attack. 



In this connection, however, we must consider the Carnivora 

 as one of the causes of final c.rt'nivliou of diminished groups of ani- 

 mals which are struggling to maiiitnin tlicinselves against adverse 

 conditions of (a) jihysic.-il (MiviromiuMit. droughts, or cold, (6) 

 changing r.HMl ^iipplv, < onipctitin,, \s idi other quadrupeds, {d) 



'tI.c al.o^," opinion, of Mom. and Klli(,t), therefore, do not 

 hold good (3) of diminished Imt.!.. u hi. l. arc unable a<le(iuately to 

 defend tlieir young, or (4) of cases win-ic ncwlv introduced Carni- 

 vora find quadrupeds unpro\ id<'d with adiMpiate means of defence, 

 as in the South American invasion from North America in the 

 upper Pliocene. 



Environment and life (including heredity and ontogeny) are 

 alwaijs reciprocal. Having considered the causes of extinction 

 which originate in the environrnenl let us pass to those which 

 originate in a lack of internal adaptation and adaptability. 



' '•The^Extiiu-tion of Species." I>rnc. Aaul. \al. Set. Phila., June, 1895, 



