19 



Zygotes, or definitive sporoblasts, which by the secretion of tough 

 membranes, or sporocysts, become spores. Within the spores 



Sporozoites are formed by the nucleus of the spore dividing into 

 two, four, and, finally, into eight nuclei, around each of which some 

 of the protoplasm of the spore becomes aggregated. 



Dissemination of the parasite — By analogy from known forms, 

 spores pass to exterior, are scattered and then swallowed accidentally 

 by an earthworm with its food, sporocysts dissolved by digesti^'e 

 juices, and liberated sporozoites bore through tissues. 



Occurrence of Gregarinidse — Invertebrate hosts, mainly insects, 

 but generalized life cycle makes them important objects of study. 

 Disseminated passively, infection of host being by way of the ali- 

 mentary canal. Majority of species probably harmless to their hosts. 



Order COCCIDIIDIA 



Cell-infesting sporozoa which usually reproduce intracellularly by 

 asexual spore formation (schizogony), as well as by true sporogony, 

 thus giving a life-cycle with an alternation of asexual and sexual 

 generations. After fertilization the oosphere forms sporoblasts 

 which may or may not be covered by a sporocyst membrane, and 

 which may each become transformed into one or several sporozoites. 

 Take as a type 



Coccidium schubergi — (See Leuckart-Chun's Chart 103, and 

 Schaudinn's explanation thereto. For detailed account see Schau- 

 dinn, '00). Intestinal parasite of a myriapod, Lithohius forficatus. 

 Infection by encysted sporozoites taken up with food. Alternation 

 of generations. 



Sporozoites released from cyst by action of digestive juices of host, 

 fig. 1. Penetration of epithelium, fig. 2. Mature sporozoite known 

 as a 



Schizont, (fig. 4), Nuclear division. Schizogony, giving rise to 

 numerous 



Merozoites, (fig. 5), as the asexual elements are called, in contra- 

 distinction to the sexually produced sporozoites. Repeated 

 schizogony. From certain merozoites develop 



Gametes — Macrogametes, (fig. 6). Microgametoblasts, (fig. 6a). 

 Maturation of the macrogametes. Formation of the microgametes 



