304 THE WORLD OF LIFE 



in turn became more varied and better adapted to resist their 

 attacks; and when the new type had become well established it 

 quickly replaced the earlier forms ; and the highly specialised 

 reptiles, unable to obtain sufficient nourishment from it, and 

 being also subject to the attacks of Camivora of increasing 

 power, and perhaps to some adverse climatic changes, quickly 

 disappeared. Then came the turn of the Mammalia, the birds, 

 and the more specialised insects, which, during this vast period, 

 had been slowly developing into varied but always rather 

 diminutive forms, the birds and mammals feeding probably 

 on insects, roots, and seeds; but, in proportion as the reptiles 

 disappeared, they were ready to branch out in various direc- 

 tions, occupying the many places in nature left vacant by these 

 animals, and thus initiated that wonderfully varied mam- 

 malian life which throughout the whole Tertiary period occu- 

 pied the earth's surface as completely, and almost as exclu- 

 sively, as the reptiles had done during the middle ages of geo- 

 logical time. 



The reactions of insects and flowers are universally ad- 

 mitted, as are those between birds and fruits ; but the broader 

 aspect of this reaction between animal and plant life as a 

 whole has not, I think, received much attention. It does, 

 however, seem to throw a glimmer of light on the very puz- 

 zling facts of the vast development of Secondary reptilian 

 life, the apparent arrest of development of mammals during 

 the whole vast period, and the rapid and abundant outgrowths 

 of the higher types both of plants and of Mammalia in the 

 Tertiary age. 



The complete metamorphosis, broadly speaking, of both 

 plant and animal life, on passing from the former to the lat- 

 ter epoch, is most startling. Such a change was, however, ab- 

 solutely essential, not only for the production of the higher 

 Mammalia and intellectual man, but also to provide for the 

 infinitely varied needs of man's material, moral, and aesthetic 

 development. The immensely varied plant-group of phanero- 

 gams has served to unlock for his service the myriad potenti- 



