362 THE RECAPITULATION THEORY 



If our difficulties are increasing, so also are our 

 means of grappling with them ; if the goal appears 

 harder to reach than we thought, on the other 

 hand its position is far better defined, and the 

 means of approach, the lines 'of attack, are more 

 clearly recognised. One thing above all is 

 apparent that embryologists must not work 

 single-handed, and must not be satisfied with an 

 acquaintance, however exact, with animals from 

 the side of development only ; for embryos have 

 this in common with maps, that too close and too 

 exclusive a study of them is apt to disturb a man's 

 reasoning power. 



I Embryology is a means, not an end. Our 

 ambition is to explain in what manner and by 

 what stages the present structure of animals has 

 been attained. Towards this embryology affords 

 most potent aid ; but the eloquent protest of the 

 great anatomist of Heidelberg must be laid to 

 heart, and it must not be forgotten that it is 

 through comparative anatomy that its power to 

 help is derived. What would it profit us, as 

 Gegenbaur justly asks, to know that the higher 

 vertebrates when embryos, have slite in their 

 throats, unless through comparative anatomy we 

 were acquainted with forms now existing in which 

 these slits are structures essential to existence ? 

 Anatomy defines the goal, tells us of the things 

 that have to be explained ; embryology offers a 

 means, otherwise denied to us, of attaining it. 

 Comparative anatomy and palaeontology must be 

 studied most earnestly by those who would turn 



