Anderson, Some aspects of Variation. 017 



or hexagonal cells, the principles of least space, power and time 

 will necessarily be involved. There are instances given by Dar- 

 w i n and others of animals taking advantage of their organs in 

 doing unus.ual work. The loss of some unknown substance may 

 render an animal sterile, that is deprive a tissue of its usual power. 

 The presence of a certain substance, a ferment, perhaps, or en- 

 zyme, may enable the animal or plant to overcome difficulties of 

 development or growth. Dimorphism or Trimorphism may be re- 

 garded as proving the power of an animal to vary. One kind 

 may maintain the characters which another requires, but lacks, 

 to reproduce. An organ falling gradually out of use might become 

 rudimentary and the unused substance may go to form some other 

 organ, one, perhaps, of a similar nature, a lost finger may lead to 

 increased growth in some other member. The loss of 2 (or 4) 

 fingers in Man may have made the present ones bigger. It is 

 common to find seeds absorbed so as to enlarge others. It is in 

 connection with limbs that one finds some of the most stimulating 

 examples of Variation and of the results of adaptibility, reflex, 

 and perception. No one denies that the manus and pes of the 

 most highly specialized have been derived from a polydactyl arran- 

 gement. Evidence in favour of this is abundantly supplied by 

 the palaeontologist and the morphologist. The differences in the 

 size of the toes and fingers depends on similar factors. Parts not 

 used are apt to atrophy and disappear thereare. In amphibia in- 

 stances of a larger number of phalanges in the fourth toe than 

 in the others. There is a prehallux present of one or more Seg- 

 ments. J. J. Schmalhausen says that the calcaneus and 

 IV Metatarsal are distinctly prochondral, and that the fourth digit 

 is longest in Pelobates. 



In Chelonia two phalanges on the innermost 

 and outermost finger, and three phalanges on the 

 middle finger. 



The coalescence of the posterior elements of the tarsus is 

 found in Emys. 



The calcancum is separate in the others, and there is a cen- 

 trale in Chelydra. Lizards have most phalanges in their fourth 

 fingers and toes, the Order being 2, 3, 4, 5, 3, for the hand from 

 within out, 



and 2, 3, 4, 5, 4, for the foot from within out. 



Crocodiles have 2, 3, 4, 4, 3 in hand, here again the fourth 

 has more phalanges than 2 and 5 Birds give 1(0), 2 or 3, and 

 1 or 2, for wing. 



Some look upon the 2nd finger as representing the persistent 

 middle finger. This is not the usual view. The pes in birds gives 

 2 > 3> 4> 5 f° r the phalanges, (one may note that in mammalia, the 

 middle digit is the principal point of purchase in simple progres- 

 sion) although the 3nd and 4th are used in ostrich the parallel 



