THE GEOLOGICAL EVIDENCES. 



alive, and that the young is nourished directly 

 from the parent has generally been considered an 

 impassable obstacle in the way of correlating these 

 animals with animals lower in the scale of organ- 

 ization than themselves. It is barely three years 

 since we had the startling announcement, made 



Australian duck-bill (Ornithorhynchus). 



independently by two investigators, and through 

 observation on two distinct animals, that at least 

 two of the mammalian types, the duck-bill and 

 the echidna, instead of developing their young in 

 the normal manner of the animals of their class, 



