8 INTRODUCTORY. 



any of the several branches of biology and need not be assigned 

 an independent place. 



Psychology and Sociology are not yet generally admitted to 

 constitute branches of biology, and it is customary and con- 

 venient to set them apart from it. The establishment of the 

 theory of evolution has clearly shown, however, that the study 

 of these sciences is inseparable from that of biology in the ordi- 

 nary sense. The instincts and other mental actions of the lower 



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animals are as truly subjects of psychological as of physiological 

 inquiry ; the complex social life of such animal communities as 

 we find, for instance, among the bees and ants are no less truly 

 problems of Sociology. 



It will be observed that in the scheme morphology and physi- 

 ology overlap ; that is, there are certain biological sciences in 

 which the study of structure and of action cannot be separated. 

 This is especially true of embryology, which considers the suc- 

 cessive stages of embryonic structure and also the modes of 

 action by which they are produced. And finally it must not be 

 forgotten that any particular arrangement of the biological sci- 

 ences must be in the main a matter of convenience only ; for it 



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is impossible to study any one order of phenomena in complete 

 isolation from all others. 



The term General Biology does not designate a particular 

 member of the group of biological sciences, but is only a con- 

 venient phrase, which has come into use for the general introduc- 

 tory study of biology. It bears precisely the same relation to 

 biology that general chemistry bears to chemistry or general 

 physics bears to physics. It includes an examination of the gen- 

 eral properties of living matter as revealed in the structures and 

 actions of particular living things, and may serve as a basis for 

 subsequent study of more special branches of the science. It 

 deals with the broad characteristic phenomena and laws of life as 

 illustrated by the thorough comparative study of a series of 

 plants and animals taken as representative types ; but in this 

 study the student should never lose sight of the fact that all the 

 varied phenomena which may come under his observation are in 

 the last analysis due to the properties of matter in the living 

 state, and that this matter and these properties are the real goal 

 of the study. 



