THE PLANT AND THE ANIMAL 



257 



gressive movements of whole cells. The spore plants 

 give us numerous illustrations of such phenomena. 

 Let us choose a few of them at random, taking them 

 mainly from among plants that we see every day. 

 If we pick up a dead fly and throw it into a glass of 

 water, we notice in two or three days a soft white 

 down, forming a kind of halo round the body of the 

 fly (% 74)- This is a mould, i.e. a microscopic fungus. 

 If we examine under the microscope its radiating 

 branches, we shall observe at their ends oblong sacks, 

 filled with colourless grains (fig. 74). If we leave some 

 of these sacks in water under the microscope and look 

 at them occasionally, we shall almost certainly catch 

 one of them at the 

 moment when its 

 end breaks and lets 

 out the grains it 

 enclosed. These 

 grains will cluster 

 at the opening. 

 We shall notice 

 that every one 

 of them has two 

 cilia attached to 

 one side. But in 

 a few moments 

 the whole mass of 

 them will quiver : 

 first one grain, then 

 another, and then 

 all of them will 

 stir, rush round as in a whirlpool and disperse, moving 

 their cilia so rapidly that they are now scarcely visible. 

 For a long time they continue to rush about, swimming 

 across the field of the microscope, knocking against 

 each other or anything else they meet, then bounding 

 back and rushing in another direction. 



R 



FIG. 74. 



