1 8 MAMMALIAN DESCENT. [Lect. I. 



off. On the other hand, in the tropics of the Old World, 

 to this day, the brothers of the old Mammoth have been 

 living in harmony with the Sun ; but they have thrown 

 away their cloaks, and bask, naked, in his beams. 



But, during great, sudden changes in the home or 

 feeding-ground of animals, the dilemma has again and 

 again been adaptation or extinction; in many cases 

 nothing short of metamorphosis has saved them from 

 death, and kept them alive in famine. 



Speaking of metamorphosis, I am brought to that 

 which is, evidently, the key to the intricate wards of 

 this long-locked-up problem — I mean the descent of 

 organic types. The metamorphosis of insects — a marvel 

 always fresh and wonderful both to the man of years 

 and to the chUd — reveals to us the practically infinite 

 possibilities of the modifications that may take place in 

 the lifetime of a single worm-like creature. 



If we were not thoroughly familiar, from our childhood, 

 with the astounding phenomena of insect-transformation, 

 if we only knew the Grub, the Pupa, and the perfect, 

 winged Imago, separately, any assertion of such a possi- 

 bility by some far-seeing biologist, would be treated with 

 contempt, and the brand of heresy would be set upon him. 



Such a developmentalist would fare as Bruce, the 

 traveller, fared, when he related his adventures, telling 

 of the sights his eyes had seen — 



" All he gets for liis harangue is — ' "Well ! 

 What monstrous lies some travellers tell.' " 



