Wilder.] 



312 



[June 21, 



or surfaces of the digits compared are quite distinct, as shown by the 

 figure. In plural homology and in mekesyntropy, the premembral sur- 

 face of the one corresponds to that of the other, the dorsal surface of 

 the one to that of the other as if both occupied the same place, or 

 were merely superposed, as with geometrical comparisons of similar 



figures ; but with the three 

 antitropical homologies, 

 corresponding parts look 

 in opposite directions; so 

 that with platetropy, the 

 right and left digits are 

 as if placed base to base, 

 or tip to tip, with hypse- 

 tropy as if placed back to 

 back or palm to palm, 

 and with meketropy as if 

 placed side by side; but 

 the two contiguous sur- 

 faces then correspond. In 

 case the normal position 

 of the membra should be 

 determined to be other 

 than it is here assumed 

 to be, a corresponding 

 change would be made 

 with the surfaces com- 

 pared together; for in- 

 stance, if the digits were 

 made to point backward 

 and the dactyls forward, 

 their bases and tips would 

 be related meketropical- 

 ly instead of platetropi- 

 cally, while their opposite 

 sides would be related 

 platetropically instead of meketropically ; and although this would 

 be a matter of little consequence as regards a single and simple part 

 like a digit, yet when we have to compare such parts as tarsus and 

 carpus, and muscular organs, misunderstanding can be avoided only 

 by regarding the membra as always in the same normal position. 



J«J J 'f 



Fig. 3. 



