EVIDENCES OF EVOLUTION 49 



along the same road, or along closely parallel 

 roads, before they diverge, each on its own 

 path of development. 



It is only in a very general way that we can 

 accept the late Professor Milnes Marshall's 

 epigram, that the individual climbs up its 

 own genealogical tree; yet there is no doubt 

 that the development of the individual is in 

 some measure interpretable as a condensed 

 recapitulation of the presumed racial evolu- 

 tion. There is no doubt that in many cases 

 the developing embryo pursues a strangely 

 circuitous path instead of progressing straight 

 towards its goal, and the only light that we 

 can throw on many instances of this circui- 

 tousness when it is not adaptive to the 

 peculiar conditions of development is the 

 light from the past. The living hand of the 

 past is upon the embryo, constraining it to 

 follow the old route of its race, and often 

 reasserting its power in trivial details, even 

 when a considerable short-cut has been made. 



Thus in the development of every reptile, 

 bird and mammal there are residues of gill- 

 clefts, sometimes imperfectly opening, which 

 have no respiratory significance whatsoever, 

 which can hardly be said to be of any use at 

 all, except that the first one becomes the 

 Eustachian tube connecting the ear with the 

 back of the mouth. There is no known inter- 



