Probably the spores, swallowed by birds, pass out in their excrement, and when eaten by an earthworm open in its gut; the freed sickle-germs can now migrate through the tissues to the seminal funnels, in the cells of which they grow, ultimately becoming free in the seminal vesicles.[103] {97}We may now pass to the classification of the group. A. TELOSPORIDIA.—Cells 1-nucleate until the onset of brood-formation, which is simultaneous. 1. GREGARINIDACEAE.—Cells early provided with a firm pellicle and possessing a complex ectosarc; at first intracellular, soon becoming free in the gut or coelom of Invertebrates. Pairing between adults, which simultaneously produce each its brood of gametes, isogamous or bisexual, which pair within the common cyst; zygotospores surrounded by a firm cyst, and producing within a brood of sickle-shaped zoospores. (i.) SCHIZOGREGARINIDAE.—Multiplying by simple fission in the free state as well as by brood-formation; the brood-cells conjugating in a common cyst, but producing only one pairing nucleus in each mate (the rest aborting), and consequently only one spore. _Ophryocystis_ A. Schn. (ii.) ACEPHALINIDAE.—Cell one-chambered, usually without an epimerite for attachment. _Monocystis_ F. Stein; _Lankesteria_ Mingazzini. (iii.) DICYSTIDAE.—Cell divided by a plasmic partition; epimerite usually present. _Gregarina_ Dufour; _Stylorhynchus_ A. Schn.; _Pterocephalus_ A. Schn. 2. COCCIDIACEAE.—Cells of simple structure, intracellular in Metazoa. Pairing between isolated cells usually sexually differentiated as oosphere and sperm, the latter often flagellate. Brood-formation of the adult cell giving rise to sickle-shaped zoospores (merozoites), or progamic and producing the gametes. Oosperm motile or motionless, finally producing a brood of spores, which again give rise to a brood of sickle-spores. (i.) COCCIDIIDAE.—Cell permanently intracellular, or very rarely coelomic, encysting or not before division; zoospores always sickle-shaped; oosperm encysting at once, producing spores with a dense cell-wall producing sickle-germs. (ii.) HAEMOSPORIDAE.—Cells parasitic in the blood corpuscles or free in the blood of cold-blooded animals, encysting before brood-formation; zoospores sickle-shaped; oosperm at first motile. _Lankeresterella_ Labbé; (_Drepanidium_ Lank.;) _Karyolysus_ Labbé; _Haemogregarina_ Danilewski.