TIME AND LIFE 135 



two. It is constantly tacitly assumed that we have before 

 us all the forms of life which have ever existed ; and 

 though the progress of knowledge, yearly and almost 

 monthly, drives the defenders of that position from their 

 ground, they entrench themselves in the new line of defences 

 as if nothing had happened, and proclaim that the new 

 beginning is the real beginning. 



Without for an instant denying or endeavouring to 

 soften down the considerable positive differences (the 

 negative ones are met by another line of argument) which 

 undoubtedly obtain between the ancient and the modern 

 worlds of life, we believe they have been vastly overstated 

 and exaggerated, and this belief is based upon certain 

 facts whose value does not seem to have been fully appre- 

 ciated, though they have long been more or less completely 

 known. 



The multitudinous kinds of animals and plants, both 

 recent and fossil, are, as is well known, arranged by 

 zoologists and botanists, in accordance with their 

 natural relations, into groups which receive the names of 

 sub-kingdoms, classes, orders, families, genera and species. 

 Now it is a most remarkable circumstance that, viewed 

 on the great scale, living beings have differed so little 

 throughout all geologic time that there is no sub-kingdom 

 and no class wholly extinct or without living representatives. 



If we descend to the smaller groups, we find that the 

 number of orders of plants is about two hundred ; and 

 I have it on the best authority that not one of these is 

 exclusively fossil ; so that there is absolutely not a single 

 extinct ordinal type of vegetable life ; and it is not until 

 we descend to the next group, or the families, that we find 

 types which are wholly extinct. The number of orders 

 of animals, on the other hand, may be reckoned at a 

 hundred and twenty, or thereabouts, and of these, eight or 

 nine have no living representatives. The proportion of 

 extinct ordinal types of animals to the existing types, 

 therefore, does not exceed seven per cent. a marvellously 

 small proportion when we consider the vastness of geologic 

 time. 



Another class of considerations of a different kind, 

 it is true, but tending in the same direction seems to 

 have been overlooked. Not only is it true that the general 

 plan of construction of animals and plants has been the 



