366 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 



extent of variability present in the species. Consequently 508 indi- 

 viduals were taken at random and their scale or scute number counted. 

 It was found that the total number of scutes in the nine bands ranged 

 from 517 to 625 and that the commonest number was about 557. In 

 order to get a definite idea of the distribution of the different types, 



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Fig. 62. — Polygon of variation for the total number of scutes in the nine 

 bands of the armadillo (Dasypus novemcinctus) , as determined by the seriation of 

 508 individuals. Class range = 8 scutes. The solid line represents the observa- 

 tional, and the broken line the theoretical, normal curve. The abscissae refer to 

 the number of scutes, and the ordinates to the number of individuals. {From 

 Newman.) 



they were arranged in a variation polygon as shown in Figure 62. On 

 the abscissa are arranged groups including individuals between 517 

 and 524 scutes inclusive, those between 525 and 532, those between 

 533 and 540, on up to a group of those from 621 to 625. All of these 

 except the last included a small class with a range of 8 scutes. This 

 arranging in classes was essential, for without it there would have been 



