BAR, SCHLEIDEN, UNGER. IO9 



I must next mention Carl Ernst Bar, the great reformer of 

 animal embryology. In a lecture delivered in 1834, entitled 

 " The Most General Laws of Nature in All Development," 

 he shows, in the clearest way, that only in a very childish 

 view of nature could organic species be regarded as perma- 

 nent and unchangeable types, and that really they can be 

 only passing series of generations, which have developed by 

 transformation from a common original form. The same 

 conception again received firm support from Baer, in 1859, 

 through a consideration of the of laws the geographical 

 distribution of organisms. 



J. M. Schleiden, who founded, thirty years ago, in Jena, a 

 new epoch in Botany by his strictly empirico-philosophical 

 and truly scientific method, illustrated the philosophical 

 significance of the conception of organic species in his inci- 

 sive " Outlines of Scientific Botany," "^ and showed that it 

 had only a subjective origin in the general law of sjpecifica- 

 tion. The difierent species of plants are only the specified 

 productions of the formative tendencies of plants, which arise 

 from the various combinations of the fundamental forces of 

 organic matter. 



The eminent botanist, F. Unger, of Vienna, was led by 

 his profound and comprehensive investigations on extinct 

 vegetable species, to a palseontological history of the de- 

 velopment of the vegetable kingdom, which distinctly asserts 

 the principle of the Theory of Descent. In his " Attempt at 

 a History of the World of Plants " (1852), he maintains the 

 derivation of all different species of plants from a few 

 primary forms, and perhaps from a single original plant, a 

 simple vegetable cell. He shows that this view is founded 

 on the genetic connection of all vegetable forms, and is 



