;o 



VARIATION 



in man. Again, while digital variation is exceedingly common 

 in chickens, it is rare in birds generally, and is almost unknown 

 in ducks and geese which have long been domesticated. 



The fallacy above alluded to seems to have arisen from the 

 fact that domesticated species are better known than wild ones, 

 and that certain variations at least are more likely to be preserved. 

 In any event they are more strongly impressed upon our atten- 

 tion. The truth seems to be that variability depends upon the 

 nature of the part and the relative stability of the species in ques- 

 tion, not upon its domestication or its place in the scale of life. 



We can therefore avail ourselves of any material bearing upon 

 the general question wherever it may be found, hoping, however, 

 for the early coming of the time when the variations within the 

 particular field of thremmatology shall be better known and more 

 accurately described. 



Asymmetrical development in symmetrical parts. The case of 

 the narwhal illustrates a fact in variation which, though seldom 

 so apparent, is doubtless often potentially present, and if so, is 

 certainly to be reckoned with by the breeder. 



In the narwhal the canine tooth (in the male only) develops 

 as a tusk, often attaining a length of seven or eight feet, or half 

 the length of the body. The peculiarity is that normally only 

 the left tusk develops, and in the few cases seen in which both 

 are developed the right tusk is spirally twisted from left to right, 

 exactly like the left tusk, and not in the opposite direction, as 

 we should expect. What is still more astonishing is that no case 

 has ever been described in which the right tusk was developed 

 alone instead of the left. Either both are developed or the 

 left one only, and in the former case they are essentially both 

 left tusks. 



SECTION V MERISTIC VARIATION IN RADIAL SERIES 



Except in the lower forms, radial series are characteristic of 

 plant rather than of animal life. In the branching of stems and 

 the parts of flowers, members of radial series are everywhere 

 about us. Their variations are always interesting (doubling of 

 flowers) and often exceedingly valuable (stooling of grain). 



