It will be noticed that in the above life-cycle no asexual multiplication occurs. These organisms, such as _Monocystis_, are known as the Eugregarines, and include the majority of the gregarines. The remainder, which have introduced schizogony into their life-cycle, are known as the Schizogregarines. [Illustration: FIG. 66.--Spores of various Gregarines. _a_, _Xiphorhynchus_. _b_, _Ancyrophora_. _c_, _Gonospora_. _d_, _Ceratospora_. (After Léger.)] There are variations in the morphology and life-cycle of gregarines besides those that have been mentioned. It is not within the scope of this book to discuss them in detail, but the following may be noted:-- Morphological differentiation of gametes may occur as in _Stylorhynchus oblongatus_ (fig. 65), which differentiation is probably of a sexual nature. The sporocyst really consists of two layers, an epispore and an endospore. Externally the spores of different gregarines show great variety in shape and markings, and spines, or long processes may be present (fig. 66). The resistant spores serve for the transmission of the gregarines from host to host. The mode of infection is contaminative, the spores expelled with the dejecta of one host being absorbed with the food of a new host. The Gregarinida may be classified as follows:-- Sub-order I.--*Eugregarinea*, without schizogony. Tribe 1.--_Acephalina_.--Without an epimerite and non-septate; often “cœlomic” (body-cavity) parasites. _E.g._: _Monocystis_, with several species parasitic in the seminal vesicles of earthworms. Many other genera parasitic in Echinodermata, Tunicata, Arthropoda, etc. Tribe 2.--_Cephalina_.--With an epimerite, either temporarily or permanently, in the trophic phase. Usually septate (except _Doliocystidæ_). Many families, genera and species. Common in the digestive tracts of insects. _E.g._: _Gregarina_, with several species, _Gregarina ovata_ in the earwig, _Gregarina blattarum_ in the cockroach, _Stylorhynchus_ in beetles, _Pterocephalus_ in centipedes, etc. Sub-order II.--*Schizogregarinea*, with schizogony. Tribe 1.--_Endoschiza_.[170]--With schizogony occurring in the intracellular phase, _e.g._, _Selenidium_ (from Annelida and Gephyrea), _Merogregarina_ (from an Ascidian). [170] See Fantham (1908), _Parasitology_, i, p. 369. Tribe 2.--_Ectoschiza_.--In which the schizont is free, and schizogony is extracellular, _e.g._, _Ophryocystis_ (from _Blaps_, a beetle), and _Schizocystis_ (from _Ceratopogon_ larva). Order. *Coccidiidea*.