CHAPTEE I 



PROTOZOA INTRODUCTION FUNCTIONS OF PROTOPLASM 



CELL-DIVISION ANIMALS AND PLANTS 



The Free Amoeboid Cell. If we examine under the microscope 

 a fragment of one of the higher animals or plants, we find in it 

 a very complex structure. A careful study shows that it always 

 consists of certain minute elements of fundamentally the same 

 nature, which are combined or fused into " tissues." In plants, 

 where these units of structure were first studied, and where they 

 are easier to recognise, each tiny unit is usually enclosed in an 

 envelope or wall of woody or papery material, so that the whole 

 plant is honeycombed. Each separate cavity was at first called a 

 "cell"; and this term was then applied to the bounding wall. 

 and finally to the unit of living matter within, the envelope 

 receiving the name of " cell-wall." In this modern sense the 

 "cell" consists of a viscid substance, called first in animals 

 " sarcode " by Dujardin (1835), and later in plants " protoplasm " l 

 by Von Mohl (1846). On the recognition of its common nature 

 in both kingdoms, largely due to Max Schultze, the latter term 

 prevailed; and it has passed from the vocabulary of biology into 

 the domain of everyday life. We shall now examine the struc- 

 ture and behaviour of protoplasm and of the cell as an introduc- 

 tion to the detailed study of the Protozoa, or better still Protista, 1 

 the lowest types of living beings, and of Animals at lai 



1 For detailed studies of protoplasm see Delage, HtrtdUe', 2nd ed 

 Henneguy, Lecons sur la Cellule, 1896 ; Verworn, General Physiolo 



ed. 1899 ; Wilson, The Cell in Development and Inheritance, 2nd ed. 1900. All 

 these books contain full bibliographies. 



2 As we shall see later, it is by no means easy to separate sharply Protozoa and 

 Protophyta, the lowest animals and the lowest plants ; and therefore in our pre- 



