MORPHOLOGY OF ANIMALS 



absolutely necessary that the student should knoiv the 

 location in the table of classification at the end of this 

 Synopsis of every group mentioned in the text^ that he 

 should see actual specimens of each of them in the museum 

 or laboratory^ and that he should study carefully the 

 figures in the text and their descriptions if he is to get any 

 proper understanding of the morphology of animals. 



B. PRINCIPLES OF MORPHOLOGY 



In comparing the structures of different organisms (Com- 

 parative Morphology) there are a few principles applicable 

 to all plants and animals. 



I. DIFFERENTIATION AND INTEGRATION 



Organizations means differentiation and integration; 

 every living thing, even the simplest, is composed of dif- 

 ferent parts (differentiation) which parts are united into a 

 single whole (integration). Many lifeless things are or- 

 ganized, that is, they are composed of different parts that 

 are united into a single whole, — as, for example, the solar 

 system, a chemical molecule, a watch or any other machine. 

 But living things are so highly and so peculiarly organized 

 that they are called "organisms." It is protoplasmic and 

 cellular organization that is distinctive of living things. 



First among the principles of comparative morphology is 

 the fact that many organisms differ in the degree and num- 

 ber of their differentiations; those in which there are rela- 

 tively few differentiations are commonly called ''lower," 

 those with many differentiations "higher" organisms. 

 1. Grades of organization from the relatively simple to the 



relatively complex, or from the low to the high, are found 



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