Chap. XX.] 



THE AMCEBA. 



355 



size the endoplast divides into two, or sometimes the endoplas- 

 tule is the first to divid-e, and then the endoplast divides also. 

 In Fig. 103, B., an amoeba is figured, in which the division 

 of the endoplast has taken place, and the two endoplasts 

 (n. n.) are widely separated. Shortly afterwards the contractile 



FIG. 103. AMCEBA AND MONADS. 



A. Amoeba. B. Amoeba undergoing fission. C. Amoeba encysted. C. 

 Monad. D. Heteroniita. E. Cyst resulting from fusion of two Heteromita. 

 F. Cyst bursting and giving rise to fluid full of germs. 



c. v. Contractile vesicle. /. Flagellmn. yu. Gubernaculum. n. Endoplast. 

 p. s. Pseudopodium. 



vesicle (c. v.) also divided, and a delicate line of division 

 seemed suddenly to make its appearance. Forty minutes 

 afterwards the two amceba were quite separate. In Fig. 103, 

 C., an amceba is shown in the encysted condition, the outer 

 layer being clear and tolerably distinct. In this case the 

 amceba subsequently resumed its usual irregular form ; but 

 it is said that in some cases there emerge from the cyst crowds 

 of minute amoebae. Conjugation is said sometimes to occur. 



Let us note that we have in the amceba a simple cell that 

 has undergone very little differentiation. That cell, however, 

 performs several functions which characterise it as a living 

 organism. It responds to external stimuli, and is therefore sen- 

 sitive in the sense in which we have before (p. xv.) used that 

 term. The responses take the form of changes of shape in the 

 coll. It receives and assimilates food : so that there must be a 



