I2 4 



AN INTRODUCTION TO ZOOLOGY 



The division of the nucleus is followed by the division of the proto- 

 plasm. A somewhat similar process of division occurs in the egg 

 of the frog which divides into two, and each of these again into two, 

 and so on, but here all the cells produced remain together and do not 

 separate as in Amoeba. 



In this production of two new individuals it should be noted that 

 only one parental organism is concerned. There is no question of a 



FIG. 38. Division in Amceba. 



A, B, C, D, four successive stages in division ; C.G., chromatin granules ; 

 C.V., contractile vacuole ; EC., ectoplasm ; En., endoplasm ; F.V., food vacuole ; 

 N., daughter nucleus ; P., pseudopodia. 



male and female parent as in the case of Rana, and so we distinguish 

 it as Asexual Reproduction. 



Another striking contrast with the reproduction in the frog is 

 also presented. When the frog's eggs have been laid and fertilised 

 both the parents remain the same individuals as before. This goes 

 on time after time until death by old age or, much more probably, 

 by mischance intervenes. _ In Amoeba, however, the mother organism 

 does not die ; it ceases to exist as an individual, but it passes on as 

 two new beings. Hence it is that some writers speak of an Amceba 

 as potentially immortal, for we have no evidence to show that it ever 

 dies of old age as do higher forms. 



We have seen, then, that Amoeba is a tiny living unit which, in 

 spite of its small size and great simplicity of structure, exhibits all 



