124 MODERN IDEAS OF EVOLUTION 



defined, we may next inquire as to the method which 

 he employs in working out his argument This may 

 be referred to three leading modes of treatment, 

 which, as they are somewhat diverse from those 

 ordinarily familiar to logicians, and are extensively 

 used by evolutionists, deserve some illustration, more 

 especially as Haeckel is a master in their use. 



An eminent French professor of the art of sleight- 

 of-hand has defined the leading principle of jugglers 

 to be that of appearing and disappearing things ; 

 and this is the best definition that occurs to me of 

 one method of reasoning largely used by Haeckel, and 

 of which we need to be on our guard when we find 

 him employing, as he does in almost every page, such 

 phrases as it cannot be doubted/ we may there 

 fore assume, we may readily suppose, this after 

 wards assumes or becomes, * we may confidently 

 Kassert/ this developed directly, and the like, which 

 in his usage are equivalent to the presto of the con 

 juror, and which, while we are looking at one structure 

 or animal, enable him to persuade us that it has been 

 suddenly transformed into something else. 



In tracing the genealogy of man he constantly 

 employs this kind of sleight-of-hand in the most adroit 

 manner. He is perhaps describing to us the embyro 

 of a fish or an amphibian, and as we become interested 

 in the curious details, it is suddenly by some clever 

 phrase transformed into a reptile or a bird ; and yet 

 without rubbing our eyes and reflecting on the 



