11' 



66 



FACTS AND FANCIES 



9 



one animal must necessarily be originally dis- 

 tinct in its properties from that which develops 

 into another kind of animal, even though no 

 obvious difference appears to us, we have no 

 ground for supposing that the early stages of 

 all animals are alike ; and when we rigorously 

 compare the development of any animal what- 

 ever with the successive appearance of animals 

 of the same or similar groups in geological 

 time, we find many things which do not cor- 

 respond — not merely in the want of links 

 which we might expect to find, but in the more 

 significant appearance, prematurely or inoppor- 

 tunely, of forms which we would not anticipate. 

 Yet the main argument of Haeckel's book is 

 the quiet assumption that anything found to 

 occur in ontogenetic development must also 

 have occurred in phylogenesis, while manifest 

 difficulties are got rid of by assuming atavisms 

 and abnormalities. 



A third characteristic of the method of the 

 book is the use of certain terms in peculiar 

 senses, and as implying certain causes which 

 are taken for granted, though their efficacy and 

 their mode of operation are unknown. The 

 chief of the terms so employed are " heredity " 

 and " adaptation." " Heredity " is usually un- 



