No. 479] EXTINCTION OF MAMMALIA 793 



from time to time one will die, and on post mortem [examination] 

 no pathological changes can be found in any of the organs, nor do 

 the hairy calculi appear in them, although their various stomachs 

 are one mass of the briar seeds." 



Living Enviko 







The features of physical 





ent such as moisture and 



desiccation, forestation and deforestation, heat and cold, cannot be 



considered by themselves or 





relation to plant life but in 



relation to the insect life which they cor 



idition and which indirectly 



becomes the barriers and evi 





terminators of mammalian 



life. 







We may first consider the influenc 



e of the iiitroduction into 



hal)itual feeding grounds of 





forms of insect life which 



render these grounds practically uninhabital)le and cither kill or 



drive the animals out. Thus 



Wallace 



^ ol)serves: "The next case 



I will give in Mr. Darwin's 





Is: 'In several parts of the 



world insects detcnnine the 





of cattle. Perhaps Para- 



guay offers the most curiou: 





' of this; for here neither 



cattle nor horstvs nor doos hiv 





n wil.l, thou-h they swarm 



soutlnvanl and nortlnvanl in ; 



1 tVral St a 



te; and Azara and Kengger 



lun.- .l.oun tl.Mt tills i. ,;,„M 







guay. ..f a certain fly which h. 

 nials when first Ix.rn. The 







they arc, must be ha})itually ( 



•he< k.Ml 1. 



>f ihe.e flies, nunicn.us as 



oth'cr paraMti. in^rtt^. II.'mk 











ic insects would })robably 



innvasc; and (hi. ^^(.u^d U-^ 



..en the 



number of the navel-fre- 



qucntiuii- flics ilien catlK" a 





^ would become feral, and 



this ^^ouU\ nrcati;. alter 



in.lee.l I 



iKue observed in parts of 



South America i the xcuctati. 





inain would lar-ely affect 



the insects, and this, as wc i 





seen in ^Mtlonlshiie, the 







e\.'r-in.T.-asi„o , in-les of 



complexiV'...'" ' 







Thv tw.)-h.)rncd rhinoceros 



(A', hico 



mis) of .Vfrica as ^^ell as 



> \\'allace, Alfreil R. Darimnism 



, 1889, p. 11 



9. 



