MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 529 



Macrogamete. An inactive (female) cell ready for fertilization. 



Microgametocyte. A mother-cell destined to form microgametes. 



Microgamete. A motile element (male), equivalent to a sperma- 

 tozoon. 



Gametes. Specialized cells destined to meet and fuse in fertili- 

 zation. 



Gametocyst. A protective covering formed by two gregarines in 

 psendo-conj ligation; not equivalent to oocyst. 



Zygote. A cell formed by the fusion of gametes. 



Oocyst. The hardened fertilization membrane which surrounds 

 the zygote and its products. 



Metagamic divisions. Divisions of the zygote leading to the 

 formation of sporoblasts and sporozoites. 



Sporoblasts. First products of the division of a zygote. Sporo- 

 zoite mother-cells. 



Sporocy.st. Hardened and resistant special capsule of a sporo- 

 blast. 



Sporozoite. A final product of metagamic divisions. 



The significance of these terms will be apparent by illustration 

 with a concrete example for which we may again use the classical 

 case of the life history of Eimeria (Coccidium) schubergi as worked 

 out by Schaudinn (1000) (Fig. 212). This is a common intestinal 

 parasite of the familiar centipede Lithobius, infection taking place 

 by feeding on contaminated food. 



Under the action of the digestive fluids in the centipede the sporo- 

 zoites are liberated from their protective capsules (oocyst and 

 sporocyst). A sporozoite penetrates an epithelial cell and grows 

 at the expense of the cell into an agamont (Fig. 212, a). When 

 fully grown the nucleus of the parasite divides several times; 

 the protoplasm by multiple division breaks up into small cells 

 about the resulting nuclei the process of nuclear and cytoplasmic 

 division to form these cells being agamogony. The host cell is 

 destroyed and the young cells, known as agametes, are liberated. 

 These agametes make their way by independent gregariform move- 

 ment to other epithelial cells which they penetrate and in which they 

 repeat the entire agamic cycle, producing in turn new agametes. 

 After five or six days, during which this agamic cycle is repeated 

 resulting in multiple infection of the epithelium, the agametes 

 develop into gamonts or prosexual individuals. Some become 

 large, food-stored cells which, after "maturation" processes form 

 macrogametes directly (e,f, g). Others form large cells with clear 

 protoplasm — microgametocytes — which after repeated nuclear divi- 

 sions give rise to a multitude of microgametes, the process being a 

 form of gamogony. Each microgamete is provided with two 

 fiagella by means of which it moves about in the intestinal fluids 

 until it comes in contact with a macrogamete (//, i, j, s). The 

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