THE ANIMAL KINGDOM 17 



but upon the tendency of the mind to pass from 

 the apparently simple to the manifestly complex, 

 and to regard the former as primitive and ancestral 

 and the latter as secondary and derivative. 



The same tendency to regard the simplest or- 

 ganisms within a phylum as the primitive and 

 ancestral forms was exhibited by the earlier mor- 

 phologists, but a more exacting scrutiny has revealed 

 that almost all these simple animals are degenerate, 

 or simplified, not the retainers of a primaeval 

 simplicity. 



We still labour under the old misapprehension 

 as to the age of the earth and of the life upon it. 

 The origins of the animal phyla belong to a past 

 submerged far below even the vast depths of the 

 oldest stratified rocks. It is said with perfect justice 

 that existing animals, including the simplest Protozoa, 

 are only the topmost twigs of the vast genealogical 

 tree of animal life, but it can be said with equal 

 justice that the oldest fossil-bearing rocks do not 

 carry us below the topmost branches. In the oldest 

 fossiliferous rocks we meet not only with typical 

 representatives of the Crustacea, a specialized 

 branch of the Appendiculate phylum, but with actual 

 families of Crustacea (Cypridae, Nebaliidae), which 

 exist at the present day, while in the next oldest 

 strata are fishes, representatives of the Vertebrata, 

 the highest type of organization in the animal 



S. A. K. 2 



