stokes.] 



254 



[Sept. 16, 



zooid, the anterior border rounded, the lateral margins almost straight, 

 tapering to the pedicle. Lorica subspherical, the anterior border slightly 

 undulate, the anterior extremity of the pedicle suddenly expanded. Pedi- 

 cle from seven to nine times as long as the lorica, hollow, its cavity con- 

 tinuous with that of the sheath ; enclosed body usually entirely filling the 

 lorica, soft, changeable in shape, not attached posteriorly to the lorica; 

 endoplasm granular, enclosing numerous, large, refractive, probably 

 amylaceous corpuscles ; tentacles irregularly distributed at the anterior 

 border, distinctly capitate, exhibiting spiral folds during their retraction ; 

 contractile vesicle apparently single, posteriorly placed near one lateral 

 border ; nucleus not observed. Length, including pedicle, y^^ to -^J^ inch. 

 Hah. — Pond water ; attached to Myriophyllum. 



Acineta acuminata, sp. nov. Fig. 27. 



Lorica broadly vasiform, slightly longer than broad, the posterior bor- 

 der rounded, the anterior continuous, obliquely truncate on each side, and 

 produced centrally in a prominent acumination, the lateral angles also 

 often acuminately prolonged ; the anterior borders on each side separated 

 by a slit-like aperture, and the front wall bearing two narrow, anteriorly 

 converging fissures, for the passage of the tentacles ; pedicle hollow, from 

 one-third to one-half as long as the lorica and communicating with its 

 cavity ; enclosed body subspherical, attached to the lorica anteriorly only 

 and there taking the form of the sheath ; tentacles fine, capitate, scarcely 

 clustered ; contractile vesicle single, spherical, situated near one side of 

 the posterior extremity ; nucleus large, subcentral ; endoplasm granular. 

 Length of lorica, -ji^ inch ; of pedicle, j J^ ^ to -^-^^-^ inch. Hah. — Pond 

 water. 



The lateral angles are sometimes produced, sometimes rounded ; and 

 occasionally one will be rounded and the other slightly produced. The 

 anterior central acumination has been present in all the forms observed. 

 That only one wall of the lorica should be pierced by the two converging 

 fissures is noteworthy. Corresponding lines on the opposite wall could 

 not be perceived, although careful search was made for them. 



Explanation of the Figures. 



Fig. 1. Hexamita spiralis. 



2. Petalomonas dorsalis. Dia- 



gram. 



3. Urceolopsis sabulosa. 



4. Trachelomonasurceolata. 



5. Anisonema solenota. 



6. Protoperidinium limbatum. 



7. Holophrya ornata. 



8. Saprophilus agitatus. 



Fig. 9. Bothrostoma undulans. 



10. Hymenostoma magna. 



11. Vorticella pusilla. Pedicle 



omitted. 



12. Vorticella aqua-dulcis. Ped- 



icle omitted. 



13. Vorticella platysoma. 



14. Opercularia aliens!. 



15. Opercularia vestita. 



