The NUCLEAR APPARATUS lies at the inner boundary of the ectoplasm. The "meganucleus" may be ovoid, elongated, or composed of two or more rounded lobes connected by slender bridges (_Stentor_, _Stylonychia_). The "micronucleus" may be single; but even when the meganucleus is not lobed it may be accompanied by more than one micronucleus, and when it is lobed there is at least one micronucleus to each of its lobes.[160] The meganucleus often presents distinct granules of more deeply staining material, varying with the state of nutrition; these are especially visible in the band-like meganuclei of the Peritrichaceae (Figs. 51, 60). At the approach of fission it is in many cases distinctly fibrillated.[161] But all other internal differentiation, as well as any constriction, then disappears; and the ovoid or rounded figure becomes elongated and hour-glass shaped, and finally constricts into two ovoid daughter-meganuclei, which, during and after the fission of the cell, gradually assume the form characteristic of the species. The micronuclei (each and all when they are multiple) divide by modification of karyokinesis (or "mitosis") as a prelude to fission: in this process the chromatin is resolved into threads which divide longitudinally, but the nuclear wall {145}remains intact. If an Infusorian be divided into small parts, only such as possess a micronucleus and a fragment of the meganucleus are capable of survival. We shall see how important a part the micronuclei play in conjugation, a process in which the old meganuclei are completely disorganised and broken up and their débris expelled or digested. The MOUTH of the Gymnostomaceae is habitually closed, opening only for the ingestion of the living Protista that form their prey. It usually opens into a funnel-shaped PHARYNX, strengthened with a circle of firm longitudinal bars, recalling the mouth of an eel-trap or lobster-pot ("Reusenapparat" of the Germans); and this is sometimes protrusible. In _Dysteria_ the rods are replaced by a complicated arrangement of jaw- or tooth-like thickenings, which are not yet adequately described. We have above noted the strong adoral trichocysts in this group.