ORGANIC STRUCTURE: MORPHOLOGICAL 31 



conspectus of animal bodily forms sufficient for a broad survey 

 of the essential data of biology. 



9«. The Organic Cell. This is either, in itself, a living 

 animal or it is the unit, or element, of which the body of a living 

 animal is made up. A Protist is usually a single organic cell. 

 The red and white blood corpuscles, or other isolated units in the 

 body of a multicellular animal, are organic cells. So are the 

 elements into which microscopical analysis can decompose the 

 tissues of all multicellular organisms. 



jdeli mj^uzhT'caw. 



cytopLoLsm 



— NiLcleohzs 

 -NujoLqvus 

 ■ Chromatijh 

 ^'CtftoplciSTn 



5 ' S 



Fig. I. — Organic Cells. 



I, Diagram of a cell ; 2, the Zoospore of an algal seaweed ; 3. a Spirillum (Bacteria) ; 4, a 

 Diatom ; 5, a Radiolarian ; 6, a Dinoflagellate ; 7, a Ciliate (5, 6, 7 are Protozoa ; 4 is a 

 Protophjte). 



Typically the cell is spherical in shape. It is bounded by a 

 cell-membrane which may form a relatively thick wall. In the 

 typical cell there is always a smaller roughly spherical body called 

 the nucleus. The substance of the cell (outside the nucleus) is 

 called cytoplasm : this we may regard as a chemically hetero- 

 geneous substance of which the constituents are water, mineral 

 salts, proteins, carbohydrates, fats, lipoids, phosphatides, etc. In 

 the cytoplasm there are usually inclusions, such as the chlorophyll 

 plastids of the cells of a green plant. In the nucleus is a 

 ground substance much the same as the cytoplasm but contain- 



