SOME GENERAL CONCLUSIONS 287 



Still, the tracing of these almost incredibly long 

 lines of descent, if they are such, is a proper, 

 though difficult, subject of scientific research, what- 

 ever may be the result. Something has been 

 attempted in this direction over limited portions of 

 time ; but a vast amount of patient labour is re- 

 quired before certainty can be attained even in this 

 department of investigation. 



When, on the other hand, we turn to the ques- 

 tion whether such lines of creation or descent have 

 given off branches leading to new types, as, for 

 instance, from Protozoa to various Crustaceans or 

 Mollusks, we are entirely destitute of facts, and the 

 statement lately made by a leading agnostic evolu- 

 tionist, that " if there is any truth in the doctrine 

 of evolution, every class of the animal kingdom 

 must be vastly older than the past records of 

 its appearance on the surface of the globe," shows 

 us that all the attempts to construct genealogical 

 trees of the descent of animals are, so far as at 

 present known, quite visionary. It seems, indeed, 

 that each leading line, as we trace it back, ends in 

 a blind alley, just where we might suppose that it 

 was about to pass into another path. This is one 

 reason of the frequent complaints as to the imper- 



