HEREDITY AND VARIATION 93 



Definite and indefinite Variation. The first point 

 in the problem of morphological variation which can 

 be investigated by observation is whether these 

 variations are definite or irregular. If variations 

 in shape are indefinite, observation will shew that 

 they are equally arranged on each side of a mean or 

 zero point; while in definite variation the majority, 

 or perhaps all, will be in one direction, either posi- 

 tive or negative. Definite colour variations will 

 shew one colour only, indefinite variations will shew 

 several colours. Much information has been ob- 

 tained on this point, and many investigators are at 

 work on the problem. Up to the present the results 

 seem to shew that variation is indefinite; but, per- 

 haps, none of the definite kinds have been examined. 



Professor W. F. Weldon, and Mr. Herbert 

 Thomson , from a large number of measurements of 

 the carapace of a crab, have shewn that the varia- 

 tions are here indefinite ; 19 and many other examples 

 are given by Dr. A. R. Wallace in his " Darwinism." 

 Nevertheless, Professor Osborn, Professor Weis- 

 mann, and a number of other biologists agree, 

 from theoretical considerations, that definite varia- 

 tions must also take place. 



The importance of this question induces me to 

 give an example of the results of my own investi- 

 gations on the variation of the leg-bones in the 

 different species of Moa, although they are not 

 conclusive. 



There are three localities from which large quan- 



19 Pro. Poyal Soc., vol. 60. p. 195; and Itep. British Assoc. 

 1898, p. 887. 



