66 MAMMALIAN DESCENT. [Lect. III. 



always some losses by drowiiiug, until the sheep learn 

 the meaning of those dark waters. 



The earth has often had her shaking fits and her 

 attacks of colic, and then the living creatures sufter 

 with their mother ; those that escape are the strongest 

 or the most cunning ; those that can " rough " it in new 

 homes, or that are deftest in escaping from danger. 

 Nature has, unconsciously, adopted this rough method 

 of culling out her weaker tribes — appointing them for 

 slaughter — and of saving the best for the increase of the 

 flock. These suggestions relate to the incoming of the 

 Eutheria, of w]iich I must treat soon ; if Nature had not 

 dispossessed the Metatheria, and placed noljler beasts in 

 their room, we ourselves — the Eutheria of the Eutheria, 

 the noblest of the noble — should have had no existence. 



I now pass from that old occupation. Husbandry, 

 to this new work, Embryology; and if the reader 

 will give me a little attention, I will show him reason 

 for believing that the Marsupial group arose from similar 

 low forms to those that gave origin to us and the nobler 

 beasts, some of which, indeed, may be transformed Mar- 

 supials ; and that the line of demarcation between the 

 nobler and less noble types does not form a perfect fence. 



In the study of nature, as every one knows, that 

 seems to be the most bewitching part in which each 

 particular observer is working ; the skeletal frame- 

 work takes the precedence with most of us. There are 

 many excellent diagnostic marks in the skeleton of the 



