376 THE HISTORY OF THE SCIENCE OF ZOOLOGY 



connected, and made other histological contributions to 

 zoology. Leeuwenhoek, a Dutch investigator, discovered 

 blood corpuscles and striated muscle fibers, watched the 

 circulation of blood in the tail of a tadpole, thus confirm- 

 ing Harvey's discovery, and described many forms of 

 Protozoa, rotifers, and hydrse hitherto unknown. Swam- 

 merdam, another Dutchman, is known to all entomologists, 

 for he studied and described the habits, metamorphoses, 

 and anatomy of many different insects, accompanying his 

 descriptions with illustrations. Just here must be men- 

 tioned the two Englishmen, Hood and Grew, who dis- 

 covered, in the tissues of plants, minute cavities filled with 

 fluid and surrounded by walls which they termed cells. 



Passing over other and lesser investigators we come to the 

 English clergyman, John Ray, who first systematized the 

 zoological knowledge already gained and put the science 

 of zoology on an organized basis. He grasped the idea of 

 species and saw the real value of a comparison of anatomical 

 characters of animals to show their true relationships, which 

 enabled him to classify animals much better than they had 

 been heretofore. 



Eighteenth century. — The year 1707 saw ushered into 

 the world the Swedish founder of modern systematic zool- 

 ogy, Carl Linne, or Linnfeus. He first established the value 

 of groups higher than species — genera, orders, and classes 

 — and used them in their proper relation to each other. 

 He also instituted the system of naming animals according 

 to the principles of the binomial nomenclature. That is, 

 each animal was given two names taken from the Latin 

 language, the first name indicating the genus and the second 

 name the species to which the animal belonged. Linnteus 

 also named and described each species of animal and 



