The sporocysts are probably ingested by the Oxycanus larvae, either with contaminated grass, or in the process of excavating the tunnel in the soil. It is assumed that the sporozoites escape from the sporocyst in the gut and enter the epithelial cells of the intestinal wall, later passing through the basal membrane and coming to lie in the body cavity, though still attached to the intestine. After the growth of the trophozoite is complete it becomes detached from the intestine and floats free in the body cavity of the larva. These free trophozoites or sporonts may then be observed to attach in pairs, at first only at one point on the circumference, but later fused into a spherical mass, with each sporont hemispherical in shape. Gametes are produced by each sporont and the dividing wall between the sporonts disappears to allow the fusion of the gametes to form zygotes, each of which gives rise to a sporocyst containing eight sporozoites. All these stages may be observed (except the intra-cellular trophozoite, which has not been seen) in the body cavity of the host larvae. The later stages, the gametocysts and the contained sporocysts, have also
Text Fig. 1—T.S. of host intestine and attached trophozoite.
B., basal membrane of intestine wall; c., connective tissue of intestine wall; e., epithelial cell of intestine wall; h., haemocyte or phagocyte; k., karyosome or endosome; n., nucleus; r., regenerative cell; t., trophozoite.
been found in the body cavity of the pupae and of both sexes of the adult insect. The only occasion on which hatching of the sporozoites from the sporocyst was observed was when sporocysts obtained from adult insects were mounted in a hanging drop consisting of the fluid part of the gut contents of the larva. On this occasion eight sporozoites were observed to emerge from a single sporocyst. The sporocysts are non-mobile and are in any case probably contained in the gametocysts until mechanical disruption of this occurs after the death of the adult insect. There is no exit from the body cavity for the gametocysts or sporocysts, and it is assumed that the sporocysts are liberated either by the disintegration of the dead body of the host or possibly passed through the intestine of birds which may devour the host insect. The host insect takes no food and excretes only the meconium after emergence. No evidence was seen of the presence of sporocysts in this meconium.