vi PREFACE. 



It is in these circumstances most desirable that tliose who 

 are not specialists in such matters should be in a position 

 to judge for themselves ; and it does not appear impossible, 

 in the actual state of knowledge, to present, in terms intel- 

 ligible to the general reader, such a view of the ascertained 

 sequence of the forms of life as may serve at once to give 

 exalted and elevating views of the great plan of creation, 

 and to prevent the deceptions of pseudo-scientists from doing 

 their evil work. Difficulties, no doubt, attend the attempt. 

 They arise from the enormous accumulation of facts, from the 

 uncertainties attending many important points, from the new 

 views constantly opening up in the progress of discovery, and 

 from the difficulty of presenting in an intelligible form the 

 preliminary data in biology and geology necessary for the 

 understanding of the questions in hand. In order, as far as 

 possible, to obviate these difficulties, the plan adopted has 

 been to note the first known appearance of each leading type 

 of life, and to follow its progress down to the present time or 

 until it became extinct. This method is at least natural and 

 historical, and has commended itself to the writer as giving 

 a very clear comprehension of the actual state of our know- 

 ledge, and as presenting some aspects of the subject which 

 may be novel and suggestive even to those who have studied 

 it most deeply. 



In selecting examples and illustrations, the writer has en- 

 deavoured to avoid, as far as possible, those already familiar 

 to the general reader. He has carefully sought for the latest 

 facts, while rejecting as unproved many things that are con- 

 fidently asserted, and has endeavoured to avoid all riiat is 



