PLATE XXV I. 



EXPLANATION. 



Fig. 



1-9. OpalINA RANARUM, Purkinge, vol. ii. p. 559. — i, Adult animalcule, x 100 ; 2-5, 

 successive phases of segmentation terminating in the production of minute 

 ovate zooids possessing but a few nuclei or endoplasts, x 100; 6, succeeding 

 encysted condition of No. 5, x 200 ; 7 and 8, successive developmental phases 

 of zooid that has re-emerged from the encysted state, the one at 7 possessing 

 but a single endoplast, and that at 8 three such structures, the lowermost 

 of which, at a, is in the act of subdividing ; 9, a young zooid with ragged 

 pseudopodium-like lateral extensions (1-8 after Ernst Zeller, 9 after T. W. 

 Engelmann). 

 lo-ii. Opalina OBTRIGONA, Stein, vol. ii. p. 562. — 10, Adult zooid, x 100; ir, minute 

 encystment, x 200 (Ernst Zeller). 



12. Anoplophrya NAIDOS, Duj. sp., vol. ii. p. 563. — Adult zooid, X 200 (Ray 



Lankester). 



13. Anoplophrya filum, C. & L., vol. ii. p. 567, x 120 (Claparfede & Lachmann). 



14. Anoplophrya prolifera, C. & L., vol. ii. p. 564. — Adult example with five 



incompletely separated posterior segments, x 1 20 (Clap. & Lach.). 



15. Hoplitophrya lumbrici, Duj. sp., vol. ii. p. 571. — Adult zooid in the act of 



dividing by transverse fission, at u, u, horny uncini, x 200 (Stein). 

 16-18. Opalina dimidiata, Stein, vol. ii. p. 561.— 16, Adult animalcule, x 100; 17, 

 minute zooid, produced through successive fission of adult unit, commencing 

 to subdivide again in a longitudinal direction ; 18, elongate zooid, containing 

 but a single endoplast, recently emerged from a minute encystment (Ernst 

 Zeller). 



19. Opalina INTESTINALIS, Ehr. sp., vol. ii. p. 562, x 100 (Ernst Zeller). 



20. Opalina ranarum, Purk., vol. ii. p. 559. — Fragment of cuticular fibrilte treated 



with acetic acid, X 200 (Zeller). 



21. Anoplophrya CLAY ATA, Leidy sp., vol. ii. p. 566, x 150 (Leidy). 



22. Hoplitophrya recurva, C. & L. sp., vol. ii. p. 573, x 130 (Clap. & Lach.). 

 23,24. Opalina CAUDATA, Zeller, vol. ii. p. 563. — Dorsal and lateral aspects, x 120 



(Zeller). 

 25. Anoplophrya cochleariformis, Leidy sp., vol. ii. p. 566, x 150 (Leidy). 

 26, 27. Anoplophrya mytili, Quenn. sp., vol. ii. p. 565. — Lateral and dorsal aspects, 



X 250 (Quennerstedt). 

 28-30. PARAMyEClUM aurelia, Miiller, vol. ii. p. 483. — 28 and 29, Lateral and ventral 

 aspects, X 200; 30, two conjugating zooids. 



