Fig. 64.—Schematic figures of conjugation and spore formation in Gregarines. For details see text. (After Calkins and Siedlecki, modified.)
Fig. 65.—Stylorhynchus oblongatus. a, cyst containing two sporonts or gametocytes, each full of gametes, those in the upper one being male. b, ripe male and female gametes. × 1,600. (After L. Léger.)
The zygote grows slightly and becomes oval or elongate, and at this period is often called the sporoblast. It then secretes an external membrane, the sporocyst. Nuclear division occurs inside the sporocyst by a series of three binary fissions (fig. 64, e), so that each sporocyst, now usually referred to as a spore, contains eight nuclei. The cytoplasm collects around each nucleus and eight vermicular sporozoites are produced within each spore (fig. 64, f), thus completing the life-cycle.
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.
