English: Ciliata.

1. Opalinopsis sepiolae, Foett.: a parasitic Holotrichous mouthless Ciliate from the liver of the Squid. a, branched meganucleus; b, vacuoles (non-contractile).

2. A similar specimen treated with picrocarmine, showing a remarkably branched and twisted meganucleus (a), in place of several nuclei.

3. Anoplophrya naidos, Duj.; a mouthless Holotrichous Ciliate parasitic in the worm Nais. a, the large axial meganucleus; b, contractile vacuoles.

4. Anoplophrya prolifera, C. and L.; from the intestine of Clitellio. Remarkable for the adhesion of incomplete fission-products in a metameric series. a, meganucleus.

5. Amphileptus gigas, C. and L. (Gymnostomaceae). b, contractile vacuoles; c, trichocysts (see fig. 2); d, meganucleus; e. pharynx.

6, 7. Prorodon niveus, Ehr. (Gymnostomaceae). a, meganucleus; b, contractile vacuole; c, pharynx with horny cuticular lining.

6. The fasciculate cuticle of the pharynx isolated.

8. Trachelius ovum, Ehr. (Gymnostomaceae); showing the reticulate arrangement of the endosarc, b, contractile vacuoles; c, the cuticle-lined pharynx.

9, 10, 11, 12. Icthyophthirius multifilius, Fouquet (Gymnostomaceae). Free individual and successive stages of division to form spores. a, meganucleus; b, contractile vacuoles.

13. Didinium nasutum, Müll. (Gymnostomaceae). The pharynx is everted and has seized a Paramecium as food. a, meganucleus; b, contractile vacuole; c, everted pharynx.

14. Euplotes charon, Müll. (Hypotrichaceae); lateral view of the animal when using its great cirrhi, x, as ambulatory organs.

15. Euplotes harpa, Stein (Hypotrichaceae); h, mouth; x, cirrhi.

16. Nyctotherus cordiformis, Stein (a Heterotriceae), parasitic in the intestine of the Frog; a, meganucleus; b, contractile vacuole; c, food particle; d, anus; e, heterotrichous band of membranelles; f, g, mouth; h, pharynx; i, small cilia.