CHAPTEE I 



rnoTOzoA — introduction — functions of protoplasm — 



CELL-DIVISION ANIMALS AND PLANTS 



The Free Amoeboid Cell.— It' 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 ca^•ity 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 tlie 

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

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

 by Yon Molil (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," 

 the lowest types of living beings, and of Animals at large. 



^ For detailed studies of protoplasm see Delage, HirediU, 2nd ed. 190:3 ; 

 Heniieguy, Lc(;ons sicr la Cellule, 1896 ; Yerworn, General Physiology, English 

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

 these books contain full Inbliographies. 



- As we shall see later, it is l>y no means easj- to separate sharjily I'rotozoa and 

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



