| | \-----v------/ +Zoophyta+ | (_Animal-Plants_) +ACŒLOMI+ Spongiæ Acalephæ (_Worms without body-cavity_) | | | | | | \------v-------/ | | | Protascus Prothelmis | | | | \-----------v---------------/ | | +Protozoa+ | (_Primæval animals_) | |/-------------^-------------\ +GASTRÆA+ | | Infusoria | | +PLANÆA+ | Gregarinæ | | | | | | +SYNAMŒBÆ+ \----v---/ | | | | \---------v--------/ +AMŒBÆ+ | +MONERA+ The first province of the Protozoa consists of the _Egg animals_ (Ovularia); we include among them all _single-celled animals_, all animals whose body, in the fully developed state, possesses the form-value of a _simple plastid_ (of a cytod or a cell), also those simple animal forms whose body consists of an aggregation of several cells perfectly similar one to another. The _Archaic animals_ (Archezoa) form the first class in the series of Egg animals. It contains only the most simple and most ancient primary forms of the animal kingdom, whose former existence we have proved by means of the fundamental law of biogenesis; they are, (1) Animal Monera; (2) Animal Amœbæ; (3) Animal Synamœbæ. We may, if we choose, include among them a portion of the still living Monera and Amœbæ, but another portion (according to the discussion in Chapter XVI.) must on account of their neutral nature be considered as Protista, and a third portion, on account of their vegetable nature, must be considered as plants. A second class of the egg animals consists of the _Gregarines_ (Gregarinæ), which live as parasites in the intestines and body-cavities of many animals. Some of these Gregarines are perfectly simple cells like the Amœbæ; some form chains of two or three identical cells, one lying behind the other. They differ from the naked Amœbæ by possessing a thick, simple membrane, which surrounds their cell-body; they can be considered as animal Amœbæ which have adopted a parasitical mode of life, and in consequence have surrounded themselves with a secreted covering.