Harold Mellor Woodcock

“ The protoplasm in the neighbourhood of each next grows out, as a projecting bud, carrying the nucleus with it. In this manner are formed a number of club-shaped bodies, the merozoites, which are at length set free from the parent-body (IV.) , leaving a certain amount of residual cytoplasm behind. By the rupture of the disorganized host-cell, [2] the fully-formed merozoites are liberated into the intestinal lumen, and seek out fresh epithelial cells. Each is more or less sickle-shaped, and capable of active movements. Once inside a new host-cell, the merozoite grows to a schizont again. ”

“ For, although any one individual only causes the death of a single host-cell, yet the number of the parasites may be so enormously increased by this means, that the entire affected epithelium may be overrun and destroyed. Thus are occasioned grave attacks of coccidiosis, characterized by severe enteritis and diarrhoea, which may end fatally. In the case of the Vertebrates, secondary causes, resulting from the stoppage of the bile ducts, also help to produce death. There is, however, one factor in the endangered animal’s favour. Schizogony cannot go on indefinitely ”

“ The effects of a Coccidian infection upon the host as a whole depend largely upon the extent to which endogenous multiplication of the parasites takes place. On the one hand, schizogony may be so limited in extent as not to cause appreciable injury to the host. This seems to be often the case in forms infecting Molluscs and Arthropods. On the other hand, where schizogony is rapid and prolonged, the results are often serious. ”

“ Sexuality may become evident at the very beginning of schizogony, as, e.g. in Adelea ovata (Siedlecki, 1899) , where the first-formed schizonts (those developed from the sporozoites) are differentiated into male and female (micro-and mega-schizonts) (see Plate II., fig. 5) . Correspondingly, the merozoites, to which they give rise, are also different (micro-and mega-merozoites) . In one or two cases sexuality appears even earlier in the cycle, and has thus been carried still farther back. ”

“ COCCIDIA, an important order of Sporozoa Ectospora, parasites possessing certain very distinctive characters. With one or two possible exceptions, they are invariably intracellular during the entire trophic life of the individual. They always attack tissue-cells, usually of an epithelium, and never blood-corpuscles. ”

“ Gregarines in which the sporozoites are naked) constitute in reality nothing more or less than a schizogonous generation of these Cephalopodan parasites, which have thus an alternation of true hosts. The ripe sporocysts from the Cephalopod are eaten by a particular crab (e.g. Portunus or Inachus, according to the parasite) , the sporozoites are liberated and traverse the mucous membrane of the intestine, coming to rest in the surrounding lymphatic layer. Here a large “cyst” is formed, projecting into the body-cavity, the contents of which give rise to a great number of merozoites. ”

“ The male elements (microgametes) are formed in a manner essentially comparable to that in which the formation of merozoites takes place. Although the details of the nuclear changes and divisions vary somewhat, the end-result is similar, a number of little nuclear agglomerations being evenly distributed at the surface (VII. ♂) Each of these elongates considerably, becoming comma-shaped and projecting from the gametocyte. Nearly all the body of the male gamete (VIII. ♂) consists of chromatin, the cytoplasm only forming a very delicate zone or envelope around the nucleus. ”

“ It is very interesting to note that, in the two last cases, unless this association of the microgametocyte with the megagametocyte occurs, neither can the former produce male elements (microgametes) nor can the female individual maturate and become ready for fertilization. (Concerning this question of association see also Gregarines.)
In sporogony, great variation is seen with respect to the number of spores and sporozoites formed; and, as in Gregarines, these characters are largely used for purposes of classification, under which heading they are better considered. ”

“ Spores polyzoic. Founded for I. rara, parasitic in the black slug (Limax cinereo-niger) . Many authors consider that Schneider was mistaken in attributing many sporozoites to this form, and would unite with it the genus Diplospora.
Fam. Tetrasporocystidae, Léger. The oocyst contains 4 spores.
Genus 1. Coccidium, [7] Leuckart. The spores are dizoic and the sporocysts rounded or oval. A very large number of species are known, mostly from Vertebrate hosts. C. cuniculi (= C. oviforme) from the rabbit (intestine and diverticula) , but also occurring sometimes in other domestic animals ”