24 RELATIVE HANK OF ANIMALS. 



as regards their higher and lower rank, some naturalists 



write their names thus : 



VERTEBRATA. 



ARTICULATA. MOLLUSCA. 



RADIATA. 



PROTOZOA. 



And here a word of explanation is due in regard to the 

 rank of animals. In one sense, all animals are alike per- 

 fect. Each is perfectly adapted to fulfill its own peculiar 

 office in the economy of nature. In this sense, every ani- 

 mal is perfect. But in regard to organization there is, as al- 

 ready stated, every grade, from those of the most extreme 

 simplicity, and with the most simple functions, to those 

 of the highest possible complication, and with the most 

 numerous, varied, and complicated functions. Now, an ani- 

 mal is higher according to its higher complication of struc- 

 ture, and hence, its more numerous and varied functions. 



PRINCIPAL TOPICS CONSIDERED IN CHAPTER I. 



Zoology defined. Origin and meaningof the name. Forms which all recognize 



as animal*. The difficulty of defining animals. Animals defined, in general 



terms . Plants denned. Movements of plants. Chief province of the Vege- 

 table Kingdom. Mode of reproduction in animals; in plants. Forms and 



grades of animals. The Animal Kingdom. Animals of all sizes. Animals 



found almost everywhere. Zoology treats of form, structure, development, etc. 



This science established by Aristotle, Linnaeus, and Cuvier. Zoology a 



science of the highest importance. The relations which animals hold to Man. 



Zoology in its relations to Man. Relations of Zoology to Geology. Zo- 

 ology as an educational branch. Lower and higher "forms of animate. Sys- 

 tems of organs in the higher animals. Functions of animals considered. 



Animals and plants composed of tissues. Tissues made up of cells. Cells de- 



fiuad. some kinds of animals only simple cells. The lowest animals even 



simpler than a cell. Protoplasm. The egg essentially a cell. Organic, and 



Inorganic bodies. Chemical composition of animal tissues ; of plant tissues. 



Kinds of animal tissues. Cellular tissue. Muscular tissue. Kinds of 



mu? cle. Striated muscle. Unstriated muscle. Nervous tissue. Number 



of kinds of animals. Impossible to study all kinds of animals one by one.- 



The most important facts and principles of Zoology learned by the study of a few 



kinds of animals. Absolutely necessary to study animals themselves. 



Classification of animals. Names of the Kinds of groups recognized. 



Croups not mere artificial contrivances. A simple illustration of the natural 



groups. The four great Branches or Types of Cuvier. The five great Brand 



now generally recognized. Vertebrate. Articulata. Mollusca. Radiata. 



Protozoa. Relative rank of these Branches. Rank of animals in general. 



