SPECIAL MORPHOLOGY AND TAXONOMY OF SPOROZOA 421 



becomes the sporoblast capsule and the zygotes di^•ide at once to 

 form sporozoites (Fig. 179). 



Other variations will appear in the discussion of the different 

 groups of Sporozoa as given in the following classification, in which, 

 following the majority of students of the Protozoa, we divide the 

 group into two classes— Telosporidia and Neosporidia— as outlined 

 originally by Schaudinn (1900). The two groups have little in 

 common besides the mode of life of parasites. The Class Telo- 

 sporidia includes those forms in which the life of the individual comes 

 to an end with sporulation. The Class Neosporidia includes those 

 forms in which sporulation occurs in internal buds during the xege- 

 tative activity of the individual, sporoblasts being carried about 

 by the still active parent cell. 



Class I. TELOSPORIDIA, Schaudinn. 



Telosporidia are Sporozoa which are invariably intracellular 

 parasites during some phase of the life cycle. A new host is infected 

 by contamination or by inoculation and the ^'oung germ— a sporo- 

 zoite— enters some cell element, an epithelial cell if the parasite is 

 one of the Coccidia, a blood element either blood corpuscle or blood 

 cell if it is one of the Htemosporidia, The adult forms of Gregarinida 

 are invariably extracellular or lumen-dwelling parasites, young, 

 growing stages alone being intracellular. Adult forms of Coccidio- 

 morpha are persistent intracellular parasites throughout ^'oung, 

 adult, and reproductive phases. Although some exceptional cases 

 occur in both groups, these are essential differences between the 

 two sub-classes Gregarinida and Coccidiomorpha. All are typically 

 uninucleate in the adult phase. 



Reproduction occurs either bj" agamogony or gamogony, the 

 latter involving fertilization. In one Order of the Gregarinida, the 

 Eugregarinida, the sporozoite grows directly into a gamont and 

 asexual reproduction is unknown. In a second Order the Schizo- 

 gregarinida, agamogony occurs either by equal division, internal 

 budding, or by multiple division. In Coccidiomorpha alternation 

 of generations is the rule and change of hosts is frequent. IMultiple 

 division is practically universal. 



In both sub-classes the zygote undergoes metagamic divisions. 

 In Gregarinida and in Haemosporidia amongst the Coccidiomorpha, 

 the sporozoites are formed directly by divisions of the zygote; in 

 Coccidia the zygote divides into sporoblasts or sporozoite-forming 

 cells. In all cases except in Hsemosporidia the sporozoites formed 

 in each such sporoblast, are enclosed in a special capsule by which 

 the yovmg organisms are protected against external conditions. 

 Ha^mosporidia are obligatory parasites in one host or other through- 

 out the entire life cycle otherwise they perish. 



