Zöology; a textbook for colleges and universities . kablefact that in spite of the low type of organization and themultitude of species, the different types of Protozoa areon the whole extraordinarily constant and of great an-tiquity. The very same species may be found in freshwaters on continents and islands, in the tropics and incool countries, at sea level and in the mountains. Con-sequently the student who believes he has a new Proto-zoan is obliged to consider in comparison the species ofthe whole world, for the animal he has discovered inNew York may have been described from Tasmania. 3.
Zöology; a textbook for colleges and universities . kablefact that in spite of the low type of organization and themultitude of species, the different types of Protozoa areon the whole extraordinarily constant and of great an-tiquity. The very same species may be found in freshwaters on continents and islands, in the tropics and incool countries, at sea level and in the mountains. Con-sequently the student who believes he has a new Proto-zoan is obliged to consider in comparison the species ofthe whole world, for the animal he has discovered inNew York may have been described from Tasmania. 3. The principal types of Protozoa may be classified Flagellatesin groups or subphyla by the use of a few simple char-acters. The Mastigophora or flagellates move by means of a slender, undulating or vibratile thread of proto-plasm called the fiagellum (little whip). In certaintypes there are two or even more of these flagella, and 188 ZOOLOGY some of these show a distinct approach to the bacteriaor other lowly organized plants. One of the commonest. A B Drawing by R. Weber, after Lcidy FIG. 36. A, Amiba diffluens. B, Amiba radiosa. Greatly magnified, n, nucleus;, contractile vacuole; , pseudopodia. The contractile vacuoles are excretoryorgans. They become filled with waste fluids and gases, which they eventually pourout on the surface of the body, contracting as they do so. Thus they possess, in avery simple form, functions of the lungs and kidneys of higher animals. They differin function from the lungs in not being connected with the absorption of oxygen,which is taken in through the surface of the body. flagellates in ponds and ditches is the elongated greenEuglena viridis. In this animal one may notice a red ..., ,„ _ . ,.,. , ,--, •:ti&---*--Z*»:?--«r-&.,;-;,:..*SS :, 9 .•.„, ^rJ^YVJJ^.*..:-! .;•-,»•••
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectzoology, bookyear1920
