GENUS NEPHROSELMIS—STYLOCHRYSALIS. 405 



the extension of its own outer wall, it assumes a comparatively enormous size. 

 Taking an ovate form it often — as shown at PI. XXII. Fig. 19;/ — occupies more 

 than half of the cavity of the parenchyma, and ultimately divides by repeated fission 

 into innumerable minute germs or microspores. By Stein this reproductive structure 

 is denominated the germ-sac or germ-sphere {^^Kehnkugd"), but may perhaps be 

 more appropriately distinguished as the sporosac. 



Genus V. NEPHROSELMIS, Stein. 



Animalcules solitary, illoricate, free-swimming ; flagella two in number, 

 of diverse size, issuing from the centre of one of the lateral borders ; 

 endoplasm enclosing two lateral pigment-bands. Inhabiting fresh water. 



Nephroselmis olivacea, Stein. Pl. XXII. Figs. 11-13. 



Body subreniform, the dorsal border convex, the ventral one concave ; 

 the two flagella of unequal length, inserted close to each other in the centre 

 of the concave ventral surface ; coloured pigment-bands extending through- 

 out the lateral peripheries ; contractile vesicle situated close beneath the 

 insertion of the flagella, two denser and apparently amylaceous corpuscles 

 in the dorsal or posterior region. Greatest length or diameter of bodies, 

 I- 1000". Hab. — Fresh water. 



In form, the animalcules of this species would seem to closely resemble those 

 of the Pleuromo7ms of Perty, but are to be distinguished from them by the possession 

 of an oral aperture, two flagella, and distinct pigment-bands. Practically, the sub- 

 reniform contour of this type may be said to be produced by the thrusting-in of the 

 anterior border of an ordinary ovate animalcule accompanied by the compensating 

 dilatation of the lateral peripheries. An example of multiplication by longitudinal 

 fission is represented in Stein's drawings of this species. 



Genus VI. STYLOCHRYSALIS, Stein. 



Animalcules not secreting a protective lorica, attached separately to 

 foreign objects through the medium of a stiff non-elastic pedicle ; flagella 

 two in number, subequal ; endoplasm enclosing two lateral pigment-bands. 

 Inhabiting fresh water. 



Stylochrysalis parasita, Stein. Pl. XXII. Fig. 22. 



Body ovate, somewhat pointed at each extremity ; supporting pedicle 

 varying from the same length to twice the length of the body ; lateral 

 pigment-bands evenly developed; contractile vesicle single, posteriorly 

 located. Length of body, without pedicle, 1-2500". 



Hab. — Pond water, attached to Eudorina elegans. 



In the examples of this species as yet simply figured and not described by Stein, 

 one animalcule is delineated as undergoing the process of multiplication by transverse 

 fission, while in all the zooids a structure which may be an eye-like pigment-spot or 

 an oral dilatation is placed at the anterior extremity. 



