DEVELOPMENT OF BIOLOGY 



455 



D. Development of the Subdivisions of Biology 



The microscopists taken collectively created an epoch in the 

 history of biology, so important is the lens for the advancement of 

 the science. Broadly speaking, we find that its development along 

 many lines during the eighteenth and particularly the nineteenth 

 century went hand in hand with improvements in the compound 

 microscope itself and in microscopical technique. Again, the mi- 

 croscopists in general and Malpighi in particular opened up so 



Fig. 294. — Louis Pasteur. 



many new paths of advance that from this period on it is not pos- 

 sible, even in the most general survey, to discuss the development 

 of biology as a whole. The composite picture must be formed by 

 emphasizing and piecing together various lines of work, such as 

 classification, comparative anatomy of animals, embryology, phys- 

 iology of plants and animals, genetics, and evolution. 



1. Classification 



Classification has as its object the bringing together of organisms 

 which are alike and the separating of those which are unlike; a 

 problem of no mean proportions when a conservative estimate to- 

 day shows nearly a million known species of animals and about a 

 quarter of a million plants — leaving out of account the myriads 

 of forms represented only by fossil remains. 



