122 The Science of Life. 



Whitman says, "Aristotle, Harvey, Wolff, and Blumen- 

 bach all traversed the same problem, and landed in the 

 same pitfall. They all faced the question of preform a- 

 tion, and discovering no natural way by which the germ 

 could come ready-made, they insisted that the germ 

 must start anew every time and from the pit of material 

 homogeneity, acquiring everything under the guidance 

 of hyperphysical agencies, assisted by the accident of 

 external conditions." Wolffs particular hyperphysical 

 agency was a vis corporis essentialis an essential 

 organic force; but any phrase is as good as another 

 in such matters The fact must be re-emphasized, that 

 until the genetic continuity which links generation to 

 generation was realized, until the origin of the germ- 

 cells with their heritage of organization was elucidated, 

 there could be no real progress in theories of develop- 

 ment. 



Karl Ernst von Baer (1792-1876) brings us close to 



modern movements and modern methods. He handled 



the problems of development with a firmness 



of grasp which far surpassed that of his 



predecessors, and has not been excelled by his most 



illustrious successors. Von Kolliker has said of his 



works, that they may be unreservedly described as the 



most important contributions to embryological literature. 



As a student of medicine at Dorpat he seems to have 

 been influenced by Burdach, who was even then (1810- 

 1814) lecturing on "the History of Life"; at Wiirzburg 

 he sat at the feet of a remarkable teacher, Dollinger, 

 who set his eager pupil to the practical study of com- 

 parative anatomy; but a perusal of Von Baer's charming 

 autobiography convinces one that, even in early days, 

 the student was much stronger than any of his masters. 

 In spite of formidable difficulties he persistently worked 

 his way towards the path of investigation which had 

 from early days organically attracted him, and as the 

 outcome of a long and arduous life he had the reward 

 of leaving a stately scientific edifice, where there had 

 been at the most only imperfect foundations. 



As to Von Baer's work, though we cannot in our 

 space do it justice, it may be noted, in the first place, 



