58 



Where is the young Trophozoite found ? 



In the sperm- morula, where it feeds and grows, ulti- 

 mately destroying the sperm- cluster. 



Give the subsequent History of the Trophozoite. 



When the trophic or vegetative stage has been com- 

 pleted and the limit of growth attained, the trophozoite 

 is adult and ripe for reproduction, and is then known as 

 a gametocyte (or sporont). 



What is the next Event ? 



Two gametocytes- associate together side by side. They 

 secrete a double- walled enclosing cyst. Their nuclei un- 

 dergo changes and divide by karyokinesis. There are 

 further repeated divisions which do not occur at the same- 

 time in each gametocyte. As the nuclei multiply, they 

 decrease in size, and when the limit has been reached and 

 division ceases, they move towards the surface of the 

 body. The body of each gametocyte now breaks up into 

 small portions, each containing a little nucleus ; and 

 these are the gametes. A certain amount of surplus or 

 residual protoplasm serves for their nourishment. The 

 body-wall of each gametocyte is dissolved, the gametes, 

 are set free and mix together. The cyst now contains 

 a crowd of lively gametes and conjugation follows. It is; 

 likely that each pair represents a gamete from each gameto- 

 cyte. The union results in the formation of a zygote (or 

 sporoblast). 



How does the Zygote or Sporoblast become a Spore ? 



It becomes oval and secretes a tough chitinous coat. 

 Its nucleus (by three successive amitotic divisions) divides 

 into eight and its protoplasm is segmented correspondingly, 

 with the result that the spore contains eight sickle-shaped! 

 or falciform sporozoites and a little residual protoplasm. 

 By the time the sporozoites have been formed the spore- 

 has become boat-shaped, rather like a diatom of the genu& 

 Navicula, and so these spores are also known as pseud o- 

 nayicellae. 



