6 PLANT-LIFE 



substance of this organism — that is, the endoplasm — 

 is seen to be granulated with tiny particles of solid 

 matter, while the ectoplasm, the outer surface or rind, 

 is devoid of granules, and evidently firmer and less fluid 

 than the granular endoplasm; yet it is highly elastic, 

 as the movements of the organism show. And con- 

 cerning these movements. They consist mainly in the 

 formation of pseudopodia, or false feet. Portions of 

 the body-substance are extended to form lobes or 

 processes, as shown in the figure. These are the pseudo- 

 podia, the extension of which enables the Amoeba to 

 slowly change its position. It is calculated it can thus 

 creep a distance of -^ inch in about an hour. Another 

 movement, within the body, is the repeated formation 

 and disappearance of a clear globule known as the 

 " contractile vacuole." This curious movement is due 

 to the gradual accumulation at a particular point in 

 the body of a drop of water which, having attained its 

 maximum, is speedily discharged. We may assume 

 that the function of the contractile vacuole is excretory. 

 A third movement is that involved in feeding. The 

 Amoeba comes across some delectable morsel of organic 

 food, such as a diatom, and proceeds to make a meal of 

 it. Pseudopodia are extemporized as a means of 

 grasping the food; in due course they reach round it, 

 retract, and the food particle is now enclosed in a food 

 vacuole in the substance of the organism. There, in 

 that species of stomach made-to-order, the food is acted 

 upon by a digestive ferment and so dispatched. 



A point of exceptional interest in the constitution of 

 the Amoeba is the nucleus. This is a little round body 

 in the endoplasm, of a somewhat mottled appearance. 



