New American Fresh-tvater Infusoria. By Dr. A. C. Stokes. 37 



only previously known species with a roughened cuticular surface), by 

 the absence of a distinctly ribbed superficies, those longitudinal elevations 

 in the European species being strongly hispid. In the present form 

 the cuticular prominences are scattered over the general surface as well- 

 marked conical monilations arising from rounded bases. 



Chrysomonas pulchra sp. nov., figs. 4, 5, 6. 



Body elongate ovate or obovate, somewhat flexible and changeable 

 in form, three times as long as broad, tapering and slightly constricted 

 posteriorly, curved toward one side anteriorly, the frontal border obliquely 

 excavate ; cuticular surface entirely covered with small, hemispherical 

 elevations ; flagellum scarcely equalling the body in length ; contractile 

 vesicle double, small, spherical, situated opposite to each other near the 

 frontal border, and contracting alternately; nucleus ovate, occasionally 

 becoming very conspicuous. Length of body 1/900 to 1/650 in. Colour, 

 green. Habitat, marsh water, with Sphagnum. 



This infusorian has the power to make conspicuous and quite rapid 

 changes in its shape, the body at times becoming remarkably plastic ; but 

 this ability is seldom exercised to any extent greater than the assump- 

 tion of an ovoid or subspherical form. 



In figs. 4 and 5 are shown two forms of the body ; in fig. 6, the 

 infusorian in optic longitudinal section. 



Zygoselmis mutdbilis sp, nov., figs. 7, 8, 9, 10. 



Normal contour of the body apparently elongate ovate, sub-cylin- 

 drical, but extremely soft, and incessantly and most irregularly changeable 

 in form ; surface longitudinally striate ; flagella two, unequal, the longer 

 equalling the extended body in length, the shorter about one-third as 

 long ; both apparently arising from the short, conical, oral fossa ; endo- 

 plasm filled with dark-bordered, colourless corpuscles of various sizes. 

 Length of the fully extended body 1/100 in. Habitat, standing water 

 from the cypress swamps of South Florida. 



The incessant alterations in the form of this curious infusorian 

 are indescribable. The metabolic movements are seemingly endless, the 

 endoplasmic corpuscles rushing from end to end of the body as it 

 extends, contracts, twists, and contorts itself. In figures 7, 8, 9, and 

 10 a few of these changes are shown. 



The food is indiscriminately animal or vegetable. The endoplasm of 

 the individuals observed contained desmids, diatoms, and in a single 

 instance, a small rotifer. 



Stromhidium gyrans sp. nov., figs. 11 and 12. 



Body turbinate or obconical, less than twice as long as broad, the 

 lateral border of the frontal margin with a conspicuous rounded elevation, 

 the posterior extremity tapering and truncate ; cuticular surface smooth, 

 except at the posterior region, where there are a few longitudinal 

 ridges which often extend slightly beyond the termination of the body ; 

 contractile vesicle apparently double, one large and situate laterally near 

 the posterior extremity, the other (?) smaller and near the frontal 



