PLA TE X LI I. 



EXPLANATION. 



Fig. 



1-3. LOXODES ROSTRUM, Ehr., vol. ii. p. 748.— I, zooid as viewed superficially, showing 

 cuticular stria;, marginal setas, and endoplastular spherules ; ph, sickle- 

 shaped pharyngeal tube, x 200 ; 2, a similar zooid more deeply focussed> 

 showing the reticulate or cancellate structure of the internal parenchyma ; 

 V, vacuolar spaces ; r, rcfringent corpuscles ; 3, indurated pharynx, x 300 

 (after Wrzesniowski). 



4. LiTONOTUS VARSAVIENSIS, Wrz., vol. ii. p. 744, X 500.—/;-, trichocysts 

 (Wrzesniowski). 



S-ii. LiTONOTUS FASCIOLA, Ehr. sp., vol ii. p. 743-— 5> lateral view, and 6, ventral 

 aspect, X 500 (Wrzesniowski) ; 7, example abnormally dilated with ingested 

 food ; 8-1 1, successive developmental phases of a single zooid (as observed 

 by the author). 



12, 13. LiTONOTUS WrzesnIOWSKII, S. K., vol. ii. p. 742.— 12, Lateral, and 13, ventral 

 aspects, X 400 ; tr, trichocysts. 



14, 15. Phascolodon vorticella, Stein, vol. ii. p. 746.— Ventral and lateral aspects, 

 X 250 (Stein). 



16-22. Chilodon cucullulus, Miill. sp., vol. ii. p. 746.— 16 and 17, Ventral and 

 lateral aspects, x 200 (Stein) ; 18, example dividing by transverse fission ; 

 19, conjugation of two independent zooids (Stein) ; 20, zooid with abnormally 

 developed pharyngeal tube, drawn from a preserved example supplied to the 

 author by Mr. Charles Stewart ; 21 and 22, pharyngeal rod-fascicles, 

 showing extended and contracted conditions during the ingestion of a diatom 

 frustule. 



23. Opisthodon NIEMECCENSIS, Stein, vol. ii. p. 750.— Ventral aspect, x 150 

 (Stein). 



24-26. IDUNA sulcata, C. & L., vol. ii. p. 752.— Dextral, sinistral, and ventral aspects, 

 X 175 (Claparede & Lachmann). 



27-30. Dysteria armata, Huxley, vol. ii. p. 752.-27, Sinistral aspect, x 250; 

 28-30, corneous elements of pharyngeal apparatus further enlarged (after 

 Huxley). 



31-33. CvPRiDiUM Lanceolatum, C. & L. sp., vol. ii. p. 754.— 31 and 32, Dextral and 

 sinistral aspects, x 350 ; 33, ventral view of posterior region, showing the 

 union of the lateral valves, and at st caudal style (Clap.irede & 

 Lachmann). 



