FREE CELLS AND EPITHELIUM. 6 



masses, the remains of tlie equatorial plate, become surrounded 

 by a clear fluid. These form the two nuclei at the poles of 

 the spindle. As soon as this has taken place the whole proto- 

 plasm constricts in the middle, and the cell divides into two. 



There are two other ways in which cells reproduce — namely, 

 by "budding" and by "endogenous cell-formation." "Bud- 

 ding" is when one of the produced cells is smaller than the 

 parent cell. In " endogenous cell-formation " we get the proto- 

 plasm and nucleus of the parent cell, splitting up internally 

 into a number of small bodies, known as "spores." These are 

 seen only in the lowest forms of life. 



The separation of groups of various cells leads to the forma- 

 tion of the different tissues. Of tissues we make out two 

 chief kinds — namely, vegetative tissues and animal-life tissues. 

 The former carry out the nourishment and maintenance of the 

 body; the latter are those tissues which are characteristic of 

 animals, and whose functions are for movement and sensation. 



Of vegetative cell-tissues there are two divisions — (1) epi- 

 thelial and free cells, and (2) connective tissues. The tissues 

 of " animal-life " are (3) muscular tissue, and (4) nervous tissue. 



1. Free Cells and Epithelium. 



(a) Free or loandering cells are those that are found iloating 

 in some fluid medium. The corpuscles of the blood and lymph 



m 



Fig. 1. — Blood Corpuscles of Vertebrata. 

 a, Of man ; h, of goose ; c, of crocodile ; d, of frog ; e, of skate. (Nicholson.) 



are excellent examples of free cells. In the invertebrate blood, 

 which is normally colourless, will be found numbers of pale 

 amoeboid bodies. In vertebrate blood these amosboid corpuscles 

 are augmented with red blood corpuscles (fig. 1), round cell- 

 discs which contain the colouring matter of blood — namely, 



