EVIDENCES OF EVOLUTION 41 



(c) It rests thirdly upon ^ __ 



Evidence, for the individual development 

 seems almost to go out of its way to reveal 

 the evolution of the race. The familiar de- 

 velopment of frog-spawn into tadpoles and 

 froglings is in some respects almost startling 

 in its recapitulation of the evolution of the 

 Amphibian race from fish ancestors an evo- 

 lution vouched for by the data of palaeon- 

 tology and comparative anatomy. 



Following the historical order, we pass 

 from the distributional evidences of evo- 

 lution whether horizontal and geographical, 

 or vertical and palseontographical to the 

 data. These are of three kinds 



at least: (1) there js^the 



i. e. of deeply-rooted structural 

 and developmental similarities; (2) there are 

 facts of classified"! that pperies 



into species, that genus is linked to genus, 

 that tentative genealogical trees are possible; 

 and (3) there is th^ occurrence of vestigial 

 s.triictiiS, of which there is no feasible in- 

 terpretation except in terms of past history. 

 HoMOLQGiES. When two or more struc- 

 tures, organs or specialized parts, in one and 

 the same organism, or in several organisms, 

 show a deep resemblance in their architecture 

 and also in their manner of development, 

 they are said to be homologous. When they 



