CHAPTER 



7 



THE INVERTEBRATE LEGIONS 



The diverse series of phyla that compose the invertebrates is so complex that the 

 subject will be treated here on the level of the largest groups— classes and orders. 

 This task in itself can be more complex than it would first appear to be, since 

 95 per cent of all of the species of animals are invertebrates. 



So huge is the invertebrate group, that no living man can say that he 

 thoroughly comprehends even a majority of their vast array. Thus, the study 

 of them is divided into a great number of subsciences— entomology for insects, 

 protozoology for protozoans, conchology for molluscs, and so on. Nevertheless, 

 comprehension of the types of invertebrates on at least a phylum and class level 

 is possible, and we believe that such a treatment is vital in understanding the life 

 of the sea. (More thorough treatments are available as listed in the Bibliography.) 



The study of invertebrates can be a fascinating thing. Because their ways of 

 life are so far removed from the realm of man, one cannot help but be 

 constantly struck by a sense of the bizarre. Most invertebrates possess very 

 limited brain power and do not vary their habits as much as do vertebrates, but 

 within the limited behavioral pattern of each lie constant surprises. The colors 

 and the beauty of form and motion of many of them are often breath-taking, and 

 their odd habits are constant sources of wonder. 



The invertebrates are united by the possession of no single characteristic, 

 but rather by the lack of one. None of them has vertebrae or a backbone. 

 Formerly, Aristotle separated invertebrates and vertebrates on the basis that 

 vertebrates possessed blood and the invertebrates supposedlv lacked it. His word 

 on this matter was accepted until only 150 years ago when invertebrates were 

 shown to possess blood, though it is frequently colorless. 



In the following pages, the major habitat and ways of life of each group 

 are given, together with brief descriptions of a few representative species. 



NONGELLULAR ANIMALS: Phylum Protozoa {first animal) 



A noncellular animal is one whose body is not di\ided into cells. Therefore, 

 within the single cell of most protozoans, all the functions of digestion, 



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