surroundings. At the same time, we know that some animals remain fixed 

 in one spot and move very Uttle, whereas some plants are rather sensitive or 

 move visibly (see illustration, p. 257). Animals usually depend upon other 

 organisms for their food, whereas most of the common plants construct food 

 out of raw materials. 



In addition to fairly distinct animals and fairly distinct plants, there are 

 many living beings that we cannot so surely classify as either plants or ani- 

 mals. The bacteria and the "slime molds" belong in this borderland. 



Among plants, as well as among animals, we find some species that we 

 consider "higher" or more complex than others. Thus we think of an insect 

 as higher than a worm or of an oak tree as higher than a palm. We can- 

 not place all the known plants in one series and all the animals in another 

 series, running from the simplest or "lowest" to the most complex or "high- 

 est." That would be like trying to arrange all people in a straight series 

 from the worst to the best, or from the smallest to the largest. We take 

 account of degrees of complexity, as well as types of structure. 



Why Must There Be So Many Names? 



Discriminations Each human being is important enough to have his 

 name distinct from all others. We do not have an individual name for each 

 particular object — each chair, each strawberry or mosquito — because in most 

 cases it is enough to use a class-name. For most people, most of the time, 

 mosquitoes are mosquitoes, wheat is wheat. Yet it is sometimes necessary 

 to distinguish. Some mosquitoes transmit malaria, some do not. We need 

 a new name whenever we make an important distinction. 



Double Names We use double names every day in speaking of per- 

 sons — Sam Brown or Sally White. Such names consist of the family name 

 and the individual, or personal, name. We also use double names to distin- 

 guish entire groups that have some resemblances, as blue-birds, black-birds, 

 and so on. The plan of using binomial or two-name designations for all 

 species, or kinds, of plants and animals was introduced in 1735 by the 

 Swedish naturalist Carl Linnaeus (1707-1778). Thus he labeled man Homo 

 sapiens (man-wise), and a certain frog Rana virescens (frog-greenish). 



What Is a Species? When we speak of a "family" of human beings 

 — the Franklins or the Hills — we include the idea that the individuals are 

 related. The Hill boys and girls have the same father and mother. The 

 father of their cousins and their own father are brothers. They have also 

 grandparents and other cousins with different family names. We say that 

 these are related to the Hill children on the mother's side. But we think of 

 all the Hills and all the millions of other human beings as of the same kjnd. 



36 



