288 EVOLUTION IN BIOLOGY. [LECT. 



vidual plants and animals are concerned, therefore, 

 evolution is not a speculation but a fact ; and it 

 takes place by epigenesis. 



"Animal . . . per epigenesin procreatur, materiam simul 

 attralrit, parat, concoquit, et eadem utitur; formatur simul et 

 augetur . . . primum futuri corporis concrementuin . . . prout 

 augetur, dividitur sensim et distinguitur in partes, non simul 

 omnes, sed alias post alias natas, et ordine quasque suo emer- 

 gentes." 1 



In these words, by the divination of genius, 

 Harvey, in the seventeenth century, summed up the 

 outcome of the work of all those who, with appliances 

 he could not dream of, are continuing his labours in 

 the nineteenth century. 



Nevertheless, though the doctrine of epigenesis, 

 as understood by Harvey, has definitively triumphed 

 over the doctrine of evolution, as understood by his 

 opponents of the eighteenth century, it is not im- 

 possible that, when the analysis of the process of 

 development is carried still farther, and the origin of 

 the molecular components of the physically gross, 

 though sensibly minute, bodies which we term germs 

 is traced, the theory of development will approach 

 more nearly to metamorphosis than to epigenesis. 

 Harvey thought that impregnation influenced the 

 female organism as a contagion ; and that the blood, 

 which he conceived to be the first rudiment of the 

 germ, arose in the clear fluid of the "colliquamentum" 

 of the ovum by a process of concrescence, as a sort 



1 Harvey, " Exercitationes de Generatione." Ex. 45, " Quaenam 

 sit pulli materia et quomodo fiat in Ovo." 



