THE LIMBS OF LIZAKDS 129 



character in certain families and species. The process 

 is an excellent example of the origin of specific 

 characters which the field naturalist may well be 

 expected to be interested in, and we therefore propose 

 to indicate very simply and briefly the views that are 

 held on the subject, taking the slow-worm as an illus- 

 tration. 



The problem may be thus stated. Seeing that the 

 earliest forms of reptiles were provided with limbs, 

 and that at the present time a large number are 

 limbless, what explanations does biology offer to 

 account for this structural change occurring in the 

 first instance, and becoming a fixed character after- 

 wards in some species ? Every field worker should be 

 familiar with modern teaching on this question, and 

 the group of lizards is a very convenient one in 

 which to indicate the views held by various schools 

 of thought. 



For our purpose all that is necessary is to indicate 

 the two main lines on which the explanations of such 

 problems run, the older or Lamarckian view, and what 

 we may describe as the modern or Darwinian view. 



The underlying universal fact which has driven 

 so many observers to give their attention to these 

 matters is the great variation that is found every- 

 where in the animal world. The systematist gives 

 expression to these variations by dividing animals into 

 orders, families, genera, and species, according to their 

 affinities and differences, thus emphasising the fact 

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