200 



Experimental Zoology 



on the other side all the shorter men between 62 and 63.9, and 

 continue in this way until all the men are classified, we find a 

 triangle-like group (Fig. 20, B). If we join the tops of the 

 columns, we get a curve that corresponds in form to the mathe- 

 matical curve of probability (Fig. 20, A). 



- 



\ 



\ 



a 



FIG. 20. 



The same result may be shown graphically in another way. 

 If we take a lot of peas and put all of a size (i.e. within certain 

 limits) in similar cylindrical jars, and then arrange the jars so 

 that the one with the medium-sized peas is in the middle, and 

 those with the next larger peas on one side according to their 

 size ; and those with next smaller peas on the other side accord- 

 ing to their size, etc., it will be found that the tops of the piles 

 will give roughly the curve of probability. In both of these cases 



