SPECIAL MORPHOLOGY AND TAXONOMY OF SPOROZOA. 423 



and black by transmitted light. Crystals of protein-like substance 

 are present in many cases, also crystals which have been identified 

 as calcium oxalate. Between endoplasm and ectoplasm, finally, a 

 system of myonemes may be found in some cases. According to 

 Schneider these form a plexus or network of fibrils around the body; 

 according to Doflein they form transverse rings about the cell and 

 in longitudinal sections can be detected only as minute circular 

 granules. Crawley, in opposition to Schewiakoff, interprets the 

 movement of gregarines as due to these circular myoneme-like fibrils, 

 the organism utilizing them very much as a snake uses its ribs. 

 Some forms, notably the Monocystidee, may be highly metabolic; 

 others move steadily in one direction a characteristic mode of pro- 

 gression which has given rise to the term gregariform movement. 



Motile forms are limited to the free types in the digestive tract 

 or body cavity. Quiescent forms are usually attached to some epi- 

 thelial cell by a portion of the gregarine known as the epimerite. 

 This is a differentiation of the periplast frequently called the epic\i:e 

 which in different species has characteristic and varied forms with 

 specialized attaching processes in the form of hooks, anchors, fila- 

 ments, etc. They are formed only by the polycystid gregarines or 

 those with more than one chamber (monocystids) . The epimerite 

 is readily discarded and left in the host cell while the adult organism 

 a gamont, lies free in the cavity of the organ. In these forms the 

 body is divided by a transverse septum which is formed by an 

 ingro^i:h of the ectoplasm, into an anterior portion termed the 

 primite, and a posterior portion called the deutomerite. The single 

 nucleus is almost invariably in the deutomerite. 



The life history varies from a relatively simple and uncomplicated 

 progression from sporozoite to sporozoite to a complex alternation 

 of generations involving different hosts. The simpler histories 

 are found in the Eugregarinida such as Monocystis species or in 

 Lankesteria ascidias (Fig. 179). The latter is a parasite of the 

 digestive tract of the ascidian Ciona intestinalis which becomes 

 infected by eating contaminated food. The sporozoites are liber- 

 ated from the sporoblasts and enter epithelial cells where they 

 develop into gamonts. The adult forms are free in the lumen of the 

 gut and are characterized by the possession of a peculiar pseudo- 

 podium-like knob which is regarded as a tactile organ. Two of 

 these adults come together in "pseudoconjugation." A delicate 

 membrane is formed and within this membrane each of the indi- 

 viduals forms a large number of gametes. From the great nucleus 

 a smaller nucleus is formed and this divides repeatedly, its products 

 passing to the periphery where small buds, each containing a nucleus 

 are pinched off as gametes. A gamete from one individual meets 

 and fuses with a gamete from the other. A fertilization membrane 

 is formed which becomes the capsule of the sporoblast. The syn- 



