PLATE XXVI. 



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). 



10-11. OPALINA OBTRIGONA, Stein, vol. ii. p. 562. 10, Adult zooid, x 100; n, 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 (Claparede & Lachmann). 



14. ANOPLOPHRYA PROLIFERA, C. & L., vol. ii. p. 564. Adult example with five 



incompletely separated posterior segments, x 120 (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 fibrillae treated 



with acetic acid, x 200 (Zeller). 



21. ANOPLOPHRYA CLAV 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. PARAM^ECIUM AURELIA, Miiller, vol. ii. p. 483. 28 and 29, Lateral and ventral 

 aspects, x 200 ; 30, two conjugating zooids. 



