REPRODUCTIVE PROCESS IN ANIMALS 59 



to it and becomes completely fused with it to form the 

 zygote (Fig. 34 (1-4)). 



In the case of Plasmodium (Fig. 35), the difference 

 between the two gametes which undergo syngamy is 

 still more marked. The one ( $ ) is as before rounded and 

 motionless, but it is also much larger in size owing to the 

 fact that its body is distended by granules of condensed 

 food-material which it has stored up in its protoplasm. 

 The other gamete is slender, very much smaller, and swims 



FIG. 35. 



Gametes of Plasmodium, the malaria microbe. 

 , Male gamete ; $ female gamete. 



with great rapidity until passing near a gamete of the first 

 type it is drawn towards it by some apparently irresistible 

 attraction and becomes merged in it to form the zygote. 



In Plasmodium we find established the conspicuous 

 sexual differences in size and appearance which are 

 characteristic of the gametes as a general rule throughout 

 the Animal Kingdom differences so marked that the 

 two types of gamete were formerly regarded as things 

 essentially different in nature and given distinct names- 

 ova and spermatozoa. Further, we can recognise other 

 features characteristic of maleness and femaleness in 

 general the active movements and roving disposition 

 of the male ; the relative inactivity, stay-at-homeness, 

 of the female, her fatal attractiveness to the male, her 

 tendency to hoard food. 



