8 COLLEGE ZOOLOGY 



the facts of zoology has been employed with the idea of organic 

 evolution in mind. 



Practically every zoologist at the present time believes that 

 the complex animals have evolved from simpler forms at some 

 period in the world's history. How this evolution has taken 

 place is still a moot question. According to the evolution theory 

 the first animals that existed on the earth consisted of a single 

 cell, and all the animals that lived at that time would now be 

 called PROTOZOA (Chap. II). These animals gave rise in some 

 way still unknown to organisms consisting of many cells (Chap. 

 III). In the course of millions of years new and more complex 

 forms were continually being evolved from older and simpler 

 animals, so that all those now existing may be arranged in an 

 ascending series constituting a sort of genealogical tree. Many 

 of the connecting links between the various groups have disap- 

 peared, but in a few cases the remains preserved in the rocks as 

 fossils give us very definite ideas of the order of evolution. 



Man is no exception in the evolutionary process, but is closely 

 allied to the anthropoid apes, and doubtless arose from an ape- 

 like ancestor. The simpler animals living to-day probably do 

 not represent ancestral forms, since they have become modified 

 in many ways. It is only safe to make general statements, such 

 as, that man has evolved from ape-like ancestors, that the birds 

 have arisen from reptile-like ancestors, and that the insects 

 have descended from worm-like ancestors. 



2. LIVING MATTER CONTRASTED WITH NON-LIVING MATTER 



All living things are either plants or animals, and have certain 

 peculiarities which separate them from non-living things. These 

 peculiarities do not all pertain exclusively to living organisms, 

 but may, to a certain extent, be attributes of non-living bodies; 

 nevertheless, when taken together, they are sufficient to deter- 

 mine whether an object is living or lifeless. The most important 

 peculiarities are as follows: - 



