XVII] THE COMPARISON OF RELATED FORMS 741 



human figure, features, and facial expression are all transformed 

 and modified by slight variations in the relative magnitude of 

 the parts is admirably and copiously illustrated (Fig. 364). 



In a tapir's foot there is a striking difference, and yet at the 

 same time there is an obvious underlying resemblance, between 

 the middle toe and either of its unsymmetrical lateral neighbours. 

 Let us take the median terminal phalanx and inscribe its outline 

 in a net of rectangular equidistant co-ordinates (Fig. 365, a). Let 

 us then make a similar network about axes which are no longer 

 at right angles, but inclined to one another at an angle of about 

 50° (6). If into this new network we fill in, point for point, 

 an outline precisely corresponding to our original drawing of the 

 middle toe, we shall find that we have already represented the 

 main features of the adjacent lateral one. We shall, however. 



_l 13A _5 



1 2 3 4 5 



Fiff. 365. 



perceive that our new diagram looks a little too bulky on one side, 

 the inner side, of the lateral toe. If now we substitute for our 

 equidistant ordinates, ordinates which get gradually closer and 

 closer together as we pass towards the median side of the toe, 

 then we shall obtain a diagram which differs in no essential 

 respect from an actual outline copy of the lateral toe (c). In 

 short, the difference between the outline of the middle toe of the 

 tapir and the next lateral toe may be almost completely expressed 

 by saying that if the one be represented by rectangular equidistant 

 co-ordinates, the other will be represented by oblique co-ordinates, 

 whose axes make an angle of 50°, and in which the abscissal 

 interspaces decrease in a certain logarithmic ratio. We treated 

 our original complex curve or projection of the tapir's toe as a 

 function of the form F (cc, ]j) = 0. The figure of the tapir's lateral 



