632 



APPENDIX B 



passerine birds — the last group including about half the modern bird 



population). 

 Class 8. Mammals. (Mammalia.) Body usually covered with hair; warm blood 

 and completely four-chambered heart; young nourished on milk from 

 mammary glands of female. 

 Subclass 1. Egg-laying Mammals. (Prototheria.) Includes the monotremes 



(duckbill, Ornithorhynchus; spiny anteater, Tachyglossus). 

 Subclass 2. True Mammals. (Theria.) The classification of this group is 



considered in some detail in the treatment which follows. 



Fig. B.l. Representative Protozoa. A to C, class Sarcodina, order Amoebina. A, Amoeba 

 proteus, a naked type. B, Difflugia oblonga, which makes a shell of sand grains. C, Arcella 

 vulgaris, which secretes a shell. D, class Mastigophora; Ceratium, a flagellate. E, class 

 Suctoria; Ephelota, with feeding "tentacles" through which it sucks the cell contents of 

 other protozoans. F to K, class Ciliata. F, Paramecium. G, Didinium, predatory on other 

 protozoans. H, Vorticella, a stalked food strainer. I, Euplotes, a "walking" species with 

 "legs" (cirri) made up of fused cilia. J, Stentor, a food strainer. K, Spirostomum, a large 

 free-swimming type. {Courtesy General Biological Supply House, Inc.) 



Phylum I. PROTOZOA (pro' to zo' a; Greek protos, "first," and zoon, 

 "animal"). 



Single-celled animals or colonies of relatively loosely aggregated cells 

 exhibiting little or no cell differentiation or division of labor, though some 

 colonies, like Volvox, 1 have differentiated germ cells. Minute, mainly 

 microscopic forms. Examples: Amoeba (Fig. 13.1), Paramecium (Fig. 

 15.2), etc. 



1 Euglena, Volvox, and Stentor may be regarded as Algae, since they contain 

 chlorophyll ; but since they possess a number of animal characteristics, they are often 

 included among the Protozoa by zoologists. These organisms are excellent examples of 

 the Protista. 



