130 BRITISH LIZARDS 



that some animals are closely related to others. But, 

 further than that, it is a matter of common know- 

 ledge that no two animals are exactly ahke, even 

 the members of the same litter, except under very 

 exceptional circumstances which we need not consider. 

 Out of a litter of half a dozen puppies, some may 

 resemble one parent, some another, some neither ; 

 while as they grow up to adult life entirely new 

 characters may make their appearance in one of them. 

 In other words, there is great variation even in closely 

 related organisms. It is the question of what causes 

 this variation in animals that gave rise to the two 

 views above mentioned. How came the wonderful 

 variety in shape, size, structure, and habits of all the 

 species of animals ? A paragraph in Mr. G. P. 

 Mudge's Text-hook of Zoology puts the matter as 

 follows : — 



" Biologists are divided into two great camps on the 

 question of the ' Origin of Species.' There is the 

 Lamarckian or older camp, and the Darwinian or 

 newer one. The former asserts that organisms are 

 profoundly modified by the necessities of their exist- 

 ence and the nature of their physical environment, and 

 that these modifications are hereditarily transmitted, 

 accumulated, and perfected with each generation. 

 The Darwinian camp, on the other hand, asserts that 

 variations are fortuitous, that they arise spontaneously 

 from some inherent cause of which we know nothing, 

 but that having arisen, they can be either advantageous 



