THE CELL-THEORY 251 



Friedrich Wolff — such the fate with which he has met. The manuals 

 of physiology tell us that he was the founder of the doctrine of 

 epigenesis — a doctrine which, in the present day, seems so plain and 

 obvious, that we do not give him much credit for it, forgetting that he 

 had to struggle against the authority of Malpighi and of Haller, and 

 the attacks of Bonnet ; influence and authority so great, that though 

 every- reader of the ' Theoria Generationis ' must see that Wolff 

 triumphantly establishes his position, yet, seventy years afterwards, 

 we find even Cuvier ^ still accrediting the doctrine of his opponents. 



It is less generally (we might say hardly at all) known that Wolff 

 demonstrated, by numerous observations on development, the doctrine 

 of the metamorphosis of plants, when Gothe, to whom it is commonly 

 ascribed, was not quite ten years old ; ^ but it seems to have been 

 wholly forgotten that he endeavoured to work out, upon the basis 

 of the strict study of histological and morphological development, 

 that " identity of structure of plants and animals '' which is the thesis 

 defended by Schwann. Had Wolff's teaching been founded upon one 

 of those clever guesses upon which an able man will often build up a 

 plausible hypothesis, we should have thought it quite unnecessary to 

 make even historical reference to him ; but the most cursory examina- 

 tion of the ' Theoria Generationis,' or of the more popular and discursive 

 exposition of his views in the ' Theorie von d. Generation,' is enougli 

 to dispel any such notion. The passage we have already quoted is 

 sufficient to show how just and accurate Wolff's ideas upon the 

 importance of the study of development, as a method, were ; and 

 the whole of his work is the laborious application of that method. 

 The parts of the calyx, of the corolla, and of the pericarp, are for 

 him " modified leaves ; '' not because certain observed modifications 

 had suggested that they might be so considered — which is the whole 

 gist of Gothe's subsequent argument — but because he had carefully 

 traced back their development, and had found that they all proceeded 

 from the same original form. The homology of the wing of the chick 

 with its leg is placed by Wolff on precisely the same basis — the only 

 one, be it observed, on which any homology can ultimately rest ; and 

 following out the argument to its legitimate conclusion, he shows that 

 the appendicular organs of plants and animals are developed after the 



^ Histoire des Sciences Naturelles. 



^ The world, always too happy to join in toadying the rich, and taking away the " one 

 ewe lamb " from the poor, persists in ascribing the theoiy of the metamorphosis of plants to 

 Gbthe, in spite of the great poet himself (see Gothe's Werke, Cotta, 1840, B. 36, p. 105 : 

 " Entdeckung eines trefflichen Vorarbeiters "), who not only acknowledges his own obliga- 

 tions to Wolff, but speaks with just wonder and admiration of the ' Theoria Generationis,' 

 the work of a young man of six-and-twenty. 



