272 BIOLOGICAL LECTURES. 



intolerable by his eagerness to give an immediate philosophic 

 explanation of objects which he had only imperfectly examined." 

 The same statement may be extended to many of his zoological 

 observations, but this is far from convincing us that his method 

 of investigation was at fault. Wolff's method, which did not 

 differ from that of the scientist of to-day, was, if anything, more 

 admirable than his observations. The very fact that he was 

 full of his Aristotelean hypothesis of epigenesis places him head 

 and shoulders above the investigators both of his day and of 

 to-day, who nai'vely believe that they are starting their investi- 

 gations on a solid foundation of facts divorced from all theory. 

 Even Sachs admits that Wolff's phytotomical work, though 

 poor from the standpoint of observation, was the most impor- 

 tant that appeared in the period between Grew (1682) and 

 Mirbel (1802), " because its author was able to make some use 

 of what he saw, and to found a theory upon it." l 



Apart from this preconceived hypothesis of epigenesis it is 

 surprising with what perfect naiveti Wolff approaches the phe- 

 nomena to be observed. Armed with his microscope, which it 

 does not require a Sachs to tell us " was of insufficient power 

 and its definition imperfect," he entered what was practically 

 an unknown domain, peopled only with the figments of the 

 predelineationists. The fascination of the growing plant and 

 developing embryo soon possessed him and never afterwards 

 left him. During his long life he returned again and again to 

 the study of the chick. Those who teach embryology year 

 after year cannot fail to appreciate Wolff's power and great- 

 ness when they observe the superficial impression left on 

 nine-tenths of the students who study the developing chick 

 in the well-equipped laboratories of to-day. 



Wolff's instruments, poor as they were, enabled him, never- 

 theless, to traverse a considerable and very significant portion 

 of the region that lies beyond the boundary of our unaided 

 vision. What he saw there at once convinced him that em- 

 boitement was a myth. We should expect so young a man as 

 Wolff was when he wrote the Theoria to do two things to 

 repeat his main thesis ad nauseam, and to be rather unsparing 



1 Sachs. History of Botany, p. 251. 



