EXPLANATION OF PLATE XLL 



Fig. 



i~9. Ophrydium versatile, Miill. sp., vol. ii. p. 735. — i and 2, Colony-stocks, natural 

 size (after Ehrenberg) ; 3, portion of a similar colony-stock, as seen in optical 

 section slightly magnified ; 4, fragment of a colony-stock with fully extended 

 zooids, showing at a a the thread-like branching pedicle with its surrounding 

 common gelatinous matrix or zoocytium z, x 100 (after Wrzesniowski) ; 

 5 and 6, extended and contracted zooids, x 200 (after Stein) ; 7, basal 

 region of three zooids of a variety in which the relatively short pedicles are 

 distinctly annulate at their distal ends (Wrzesniowski) ; 8, fragments of a 

 colony-stock treated with haematoxylin and osmic acid, showing at a the 

 urceolate cavities in the zoocytium into which the zooids retreat ; i>, a re- 

 tracted zooid ; and c, the pedicle ; the lines at d indicate the boundaries of 

 the zoocytial element exuded by the individual zooids, x 1 50 (Wrzesniowski) ; 

 9, a detached free-swimming zooid having a posteriorly developed supple- 

 mentary girdle of cilia. 



10-17. Ophrydium Eichornii, Ehr., vol. ii. p. 737. — 10, a moderate-sized colony-stock 

 with fully extended zooids, as observed by the author, x 50 ; 11, a fragment 

 of the same stock with, ata,^, contracted zooids, X 150; 12, a zooid with 

 posteriorly developed ciliary girdle preparing to enter upon the free-swimming 

 state ; 13, a zooid exhibiting the rare phenomenon of subdivision by trans- 

 verse fission, the line at /r indicating the region of separation ; 14, a detached 

 free-swimming zooid; 15 and 16, whole and portion of a normal zooid 

 X 400 (as delineated by Wrzesniowski) ; or, oral entrance ; v, vestibular 

 fossa; pA, pharynx; (v, oesophageal tube; 17 and 18, outlines of the 

 contractile vesicle. 



19-21. Ophrydium sessile, S.K., vol. ii. p. 738. — 19, colony-stock attached to vegetable 

 filament, natural size ; 20, a colony-stock with fully extended zooids, 

 X 100; 21, a similar stock with the zooids retracted within their common 

 gelatinous zoocytium. 



22, 23. Ophionella picta, S.K., vol. ii. p. 734. — 22, extended, and 23, contracted zooid, 

 X 300. 



