Lect. III.] LINKS IN THE CHAIN OF LIFE. 73 



It now has to be shown, in the interests of biology, 

 that these are not present in the Marsupials as absolute 

 characters, and that they are not formed here, either 

 for the first or the last time. In other words, they are 

 mere specialised modes of structure, quite familiar to 

 the student of the oviparous t}^Des (either lower or 

 higher), and they do not die out suddenly, but reappear 

 in the Eutherian types that are far above them in 

 zoological height. 



Every element of the skeleton of any of these classes, 

 however inconspicuous, is a link in a very long chain, 

 and often to the morphologist a golden link, very 

 beautiful and valuable, suggesting to him origins and 

 ends that would have been unintelligible but for some 

 such small points of bone or nodules of cartilage. On 

 the other hand, the proud conservative, who would 

 isolate himself upon his human throne, must not think 

 that we are removing biological landmarks, we are 

 merely showing him that they never existed. 



I will now take these ten diagnostics one by one, 

 and look at them in their rise and in their progress. 



But let me not be misunderstood ; their rise cannot 

 be seen by us in any actual progenitors of these Meta- 

 tlieria, nor their progress in t}^es that have arisen from 

 them. That is absolutely impossible in the nature of 

 the case. The lower types are mere survivals of races 

 more or less on a level with the various supposed stages 

 through which a Metatherian must have passed to 



