104 EVOLUTION OF TO-DAY. 



doms which now exist. If now we leave out of 

 account those forms which, having no hard parts, 

 could not have been preserved, such as worms, etc., 

 we find a large majority of the groups have been 

 preserved. About five sixths of the orders, nearly 

 an equal proportion of sub-orders, a great many 

 families, some genera, and it has been claimed that 

 some of our present species, are known to have 

 been in existence during the Silurian age. It is 

 truly remarkable to find such a very large portion 

 of existing groups represented in the earliest fauna 

 of which we have any knowledge. When we re- 

 member the great imperfection of our knowledge of 

 these early animals, the difficulty here arising be- 

 comes somewhat formidable. Still more forcible 

 does this difficulty become as we realize that the 

 diversity of this early life is increasing as the record 

 is more carefully studied. The tendency of the late 

 years of paleontology seems to indicate that if our 

 record were more perfect, it would be found that 

 nearly all our existing forms, down to groups as 

 small as families, were represented in the Silurian 

 age. The vertebrates have, however, nearly all de- 

 veloped since that time. And when we compare 

 the great advance of this sub-kingdom with the 

 small advance of all others, the contrast is very 

 striking. Such a result is certainly one which evo- 

 lution would not lead us to expect. 



It must be noticed, however, that this concession 

 to the Silurian fauna is too great, since this age 

 lasted a very long time, and many of these modern 

 families did not appear till toward its close. Bv the 



