276 Sporozoa 



Nina gracilis (37). The result is a partition separating the two groups of 

 gametes except for a short time in which the microgametes are passing 

 through to join the macrogametes. The cuticular sac of the microgameto- 

 cyte, which contains a milky residue after completion of gamogony and 

 migration of the microgametes into the other compartment, remains as 

 a so-called "pseudocyst." As the spores approach maturity, the pseudocyst 

 increases in volume, apparently through accumulation of gases, and 

 serves as a float if the gametocyst has been deposited in sufficient water. 

 The increasing internal pressure eventually ruptures the gametocyst. 



In contrast to the Ophryocystidae, in which each gamont yields one 

 functional gamete (Fig. 6. 5, B, C), most gregarines produce many gam- 

 etes. In certain species, the gametes are obviously of two kinds (Fig. 

 6. 3, E-J, M-O), the microgamete being the smaller and sometimes bear- 

 ing a flagellum. Even in apparent isogamy, it is sometimes possible to 

 distinguish two types of gametes on the basis of cytoplasmic inclusions 

 (Chapter II). Comparable differences in inclusions have been noted in the 

 two gamonts within a gametocyst, as in Cephaloidophora communis (5). 



As a rule, the gametes fuse completely in syngamy. Hyaolsporina 

 cambolopsisae (14) is an exception in which only the nucleus of the micro- 

 gamete enters the macrogamete (Fig. 6. 3, M). Soon after syngamy the 

 zygote of most gregarines encysts. Within the oocyst membrane, the zy- 

 gote divides into sporozoites and the oocyst thus becomes a spore. Poro- 

 spora is an unusual genus in which no oocyst membrane is secreted, and 

 sporozoites are thus not found in spores (42). The spores (Fig. 6. 4, A-Q) 

 may be spindle-shaped, ovoid, cylindrical, or spherical in different species 

 and are usually symmetrical, although asymmetrical or sometimes hetero- 

 polar types are produced by certain gregarines. The membrane is com- 

 monly smooth, although it may be equipped with long or short spines. 



In most gregarines, the spores escape from the gametocyst by rupture 

 of the membrane. In certain genera, however, one or more tubular 

 sporoducts (Fig. 6. 4, R, S) are extruded from the wall of the mature 

 gametocyst. The sporoducts in Gregarina develop as tubular structures 

 extending inward from the gametocyst membrane and are everted shortly 

 before sporulation (2). Spores extruded through such sporoducts are 

 typically enclosed in mucous sheaths to form chains (Fig. 6. 4, P). 



In parasites of the digestive tract, spores (or sometimes young game- 

 tocysts, or even gamonts in syzygy, depending upon the species) are 

 eliminated with the feces of the host. For species living in the coelom or 

 analogous body cavities, the distribution of spores may be more com- 

 plicated. The life-cycle of Gonospora is correlated with the breeding 

 habits of its host (46). Gamogony and the production of spores coincide 

 with spawning in the polychaete host, a circumstance which insures shed- 

 ding of spores from the coelom along with spermatozoa or ova. As for 

 Monocystidae in the seminal vesicles of earthworms, spores have been 



