OF ORGANIC NATURE. ' 49 



which contains fossil remains mixed up -with those 

 of the present forms of life, and I doubt very 

 much whether your uninstructed eyes would lead 

 you to see any vast or wonderful diflPerence be- 

 tween the two. If you looked closely, you would 

 notice, in the first place, a great many things very 

 like animals with which you are acquainted now : 

 you would see differences of shape and proportion, 

 but on the whole a close similarity. 



I explained what I meant by Orders the other 

 day, when I described the animal kingdom as being 

 divided in sub-kingdoms, classes, and orders. If 

 you divide the animal kingdom into orders, you 

 will find that there are above one hundred and 

 twenty. The number may vary on one side or the 

 other, but this is a fair estimate. That is the sum 

 total of the orders of all the animals which we know 

 now, and which have been known in past times, and 

 left remains behind. 



Now, how many of those are absolutely extinct ? 

 That is to say, how many of these orders of ani- 

 mals have lived at a former period of the world's 

 history, but have at present no representatives ? 

 That is the sense in which I meant to use the word 

 " extinct.'' I mean that those animals did live on 

 this earth at one time, but have left no one of their 

 kind with us at the present moment. So that esti- 

 mating the number of extinct animals is a sort of 

 way of comparing the past creation as a whole with 

 the present as a whole. To make that clear, I have 

 written in red ink on these diagrams the names of all 

 those extinct orders, and in black ink the names of 



