Harold Mellor Woodcock

“ Around this some of the cytoplasm condenses, the rest forming a residuum. The sporoblast or gamete thus formed is completely isogamous and normally conjugates with the like one from the other associate, when a single zygote results which becomes a spore containing eight sporozoites, in the ordinary manner. Sometimes, however, the septum between the two halves of the cyst does not break down, in which case parthenogenesis occurs, each sporoblast developing by itself into a small spore. ”

“ In certain coelomic Gregarines, on the other hand, which remain in very close relation with the host’s tissues, little or nothing of an encystment-process on the part of the parasites is recognizable, the cyst-wall being formed by an enclosing layer of the host (Diplodina) .
The nuclear changes and multiplication which precede sporoblast-formation vary greatly in different Gregarines and can only be outlined here. In the formation of both sets of sexual elements (gametes) there is always a comprehensive nuclear purification or maturation. ”

“ In other cases, again, the entire sporont-nucleus proceeds to division, and the distinction between somatic and germinal portions does not become manifest until after nuclear multiplication has continued for some little time, when certain of the daughter-nuclei become altered in character, and ultimately degenerate, the remainder giving rise to the sporoblast-nuclei (Diplodina, Stylorhynchus) . Even after the actual sporoblasts (sex-cells) themselves are constituted, their nuclei may yet undergo a final maturation (e.g. Clepsydrina ovata) ”

“ Nevertheless, in no case does true encystment occur, the sex-cells being developed practically free. The female gametes are large and egg-like; the males, minute and sickle-like, but with no flagellum and apparently non-motile. While many of the zygotes (“amphionts”) resulting from copulation pass out to the exterior, to infect a new host, others, possessing a more delicate investing-membrane, penetrate in between the intestinal cells, producing a further infection (auto-infection) . Numerous sporozoites are formed in each zygote. ”

“ The two conjugating elements unite completely, cytoplasm with cytoplasm and nucleus with nucleus, to form the definitive sporoblast or zygote. The protoplasm assumes a definite outline, generally that of an ovoid or barrel, and secretes a delicate membrane, the ectospore. This subsequently becomes thickened, and often produced into rims, spines or processes, giving rise to the characteristic appearance of the Gregarine spore. Internal to the ectocyst, another, thinner membrane, the endocyst, is also laid down. ”

“ In the vast majority of Gregarines, however, the life-cycle is limited to gametogony and sporogony. A very general, if not indeed universal, prelude to gametogony is the characteristic and important feature of the order, known as association, the biological significance of which has only lately been fully brought out (see H. M. Woodcock [31] ) . In normal association, two individuals which are to be regarded as of opposite sex, come into close contact with each other and remain thus attached. The manner in which the parasites join varies in different forms ”

“ This view is supported by the fact that certain coelomic forms, like Diplodina and others, which either lack muscle-fibrils or else show no ectoplasmic differentiation at all, are non-motile. The endoplasm, or nutritive plasm, consists of a semi-fluid matrix in which are embedded vast numbers of grains and spherules of various kinds and of all sizes, representing an accumulation of food-material which is being stored up prior to reproduction. The largest and most abundant grains are of a substance termed para-glycogen, a carbohydrate ”

“ The couple (syzygy) thus formed may proceed forthwith to encystment and sporoblast-formation (Lankesteria, Monocystis) , or may continue in the trophic phase for some time longer (Gregarina) . In one or two instances (Zygocystis) , association occurs as soon as the trophozoites become adult. This leads on to the interesting phenomenon of precocious association (neogamy) , found in non-motile, coelomic Gregarines (e.g. Cystobia, Diplodina and Diplocystis) , in which the parasitism is most advanced. Woodcock (loc. cit.) ”

“ Association is very primitive in character and indiscriminate; it takes place indifferently between individuals which will give rise to gametes of the same or opposite sex. Often it is only temporary; at other times it is multiple, several adults becoming more or less enclosed in a gelatinous investment. ”

“ The favourite habitat is either the intestine (fig. 1) or its diverticula (e.g. the Malpighian tubules) , or the body-cavity. In the latter case, after infection has occurred, the liberated germs at once traverse the intestinal epithelium. ”

“ The body never possesses an epimerite and is non-septate. Chiefly coelomic parasites of “worms,” Holothurians and insects.
The Aseptata have not been so completely arranged in families as the Septata. Léger has distinguished two well-marked ones, but the remaining genera still want classifying more in detail. Fam. Gonosporidae, with Gonospora, Diplodina; and Urosporidae, with Urosopora, Cystobia, Lithocystis, Ceratospora; the genera Monocystis, Diplocystis Lankesteria and Zygocystis probably constitute another ”

“ Léger thinks only the deutomerite becomes thus segmented, the protomerite remaining small and undivided. The nucleus remains single, so that there is no question as to the unicellular or individual nature of the entire animal.
The general cytoplasm usually consists of distinct ectoplasm and endoplasm, and is limited by a membrane or cuticle (epicyte) , secreted by the former. The cuticle varies considerably in thickness, being well developed in active, intestinal forms, but very thin and delicate in non-motile coelomic Minute structure. forms (e.g. Diplodina) . ”

“ L. Léger, “Recherches sur les Grégarines,” Tabl. zool. 3, p. i., 22 pls. (1892) ; 13. L. Léger, “Contribution à la connaissance des Sporozoaires, &c.,” Bull. Sci. France, 30, p. 240, 3 pls. (1897) ; 14. L. Léger, “Sur un nouveau Sporozoaire (Schizocystis) , &c.,” C.R. Ac. Sci. 131, p. 722 (1900) ; 15. L. Léger, “La Reproduction sexuée chez les Ophryocystis,” t. c. p. 761 (1900) ; 16. L. Léger, “Sur une nouvelle Grégarine (Aggregata coelomica,) , &c.” op. cit. ”