THE GROWTH AND SCOPE OF BIOLOGY 13 



animals and plants which Linnaeus knew are described and named. 

 So accurate are the descriptions that many of his species are recognizable 

 today, and his names for them are still applied. 



Foundations of Modem Biology. — Naturalists of a certain stamp have 

 always found the classification of objects a fascinating occupation, and 

 Linnaeus had many followers. For the most part they were less able than 

 he, and their labors often degenerated into an attempt to discover and 

 name as many species as possible. Because of this tendency, classifica- 

 tion suffered a degree of disrepute. Moreover, there were many other 

 features of living things to engage attention. Discoveries were made 

 and theories formulated in nearly all the fields of biology. The phys- 

 iology of sense organs and the nervous system was studied. Embryology, 

 the science of development of the individual, was greatly advanced. 

 The process of fertilization of eggs by spermatozoa came gradually to 

 be understood, and it was found that some eggs could develop without 

 the intervention of the male cells. The existence of sex in plants was 

 recognized, and some crosses were made to ascertain the course of 

 heredity. Mutilated animals were observed to regenerate their missing 

 parts. Comparisons of the structure of various animals foreshadowed 

 the comparative anatomy of the next century. The behavior of the 

 castes of social insects was studied, marking the beginning of animal 

 psychology. In the sister science of chemistry, the nature of oxygen 

 and carbon dioxide was discovered, and naturalists began to see their 

 relation to the respiration of animals. Vague ideas of change of species, 

 implying concepts of evolution, began to be put forth. 



With this increase in the factual phase of biology, philosophy declined ; 

 and with the rising tendency to limit theory to what could be reasonably 

 supported by the ascertained facts, biology entered upon what may be 

 regarded as its modern period. This period corresponds roughly to the 

 nineteenth and twentieth centuries. It witnessed the rise of comparative 

 anatomy, the discovery of cells, the development of embryology and 

 cytology, the general acceptance of the evolution doctrine, the rapid 

 increase in the use of the experimental method, research in heredity, the 

 study of the general physiology of protoplasm, and specialization in 

 several of the narrower fields of biology. 



Comparative Anatomy. — The earliest well-defined modern trend was 

 in the field of comparative anatomy. The founder of this branch of 

 biology was Georges Cuvier (1769-1832) (Fig. 9). Cuvier possessed a 

 natural interest in living things and, being a clever draughtsman, had 

 made pictures of many of the animals he studied. Some of these pictures, 

 exhibited in Paris, won him a professorship of comparative anatomy there. 

 His rise was rapid, and mmierous honors were bestowed upon him. 

 Cuvier's comparative anatomy differed from all previous brands in that 



