276 BIOLOGICAL LECTURES. 



most important proofs of epigenesis. We may conclude from 

 it that the organs of the body have not always existed, but have 

 been formed successively : no matter how this formation has 

 been brought about. I do not say that it has been brought 

 about by a combination of particles, by a kind of fermentation, 

 through mechanical causes, through the activity of the soul, 

 but only that it has been brought about." 



Remaining within the province of observation which he 

 staked out for himself, and pursuing his excellent method, 

 Wolff was not only able to undermine the theoretical edifice of 

 the predelineationists, but also to lay the foundations for future 

 structures of great promise. Thus all conscientious investiga- 

 tion with good methods leads to subordinate facts of value 

 besides the main line of facts accumulated in support of the 

 theory in hand. Wolff was a biologist in the true sense of 

 the word. He regarded plant and animal life as but slightly 

 different aspects of a single set of phenomena. It can be 

 shown that he anticipated to some extent the modern theories 

 of protoplasm and the cell. 1 According to Sachs " it was 

 Wolff's doctrine of the formation of cellular structure in plants 

 which was in the main adopted by Mirbel at the beginning of 

 the present century," and "the opposition which it encountered 

 contributed essentially to the further advance of phytotomy." 2 



The theory of the metamorphosis of plants, usually attrib- 

 uted to Goethe, was clearly expressed by Wolff. In fact, Wolff 

 seems to have had clearer notions on the subject than Goethe, 

 according to Schleiden's statement. 



To embryology Wolff made many valuable contributions, 

 not the least of which was his description of the formation of 

 the intestinal tract of the chick. This work was styled by 

 Carl Ernst von Baer " die grosste Meisterarbeit, die wir aus 

 dem Felde der beobachtenden Naturwissenschaften kennen." 

 It was published in Latin in the twelfth and thirteenth volumes 

 of the St. Petersburg Commentaries, where it lay buried and 

 forgotten till it was unearthed and translated into German by 



1 Cf. Huxley. 



2 Sachs. Hist, of Botany, p. 250. For the relations of Wolff's views to those 

 of Schleiden and Schwarm, see Huxley, The Cell Theory. 



