Maskell. — On Freshwater tnfusoria. 1 1 



The remarkable slenderness and great length of the stem 

 clearly distinguish this species. In some specimens examined 

 the stem became, near its base, almost hair-like, "with scarcely 

 any dilation until at the commencement of the peristome. The 

 bhieish-green colour, conspicuous striae, and scarcely-expanded 

 peristome-edge are also distinctive. The fringe above men- 

 tioned, denoting approaching division, is a character delineated 

 also in Stentor polymorphus, Mviller (Kent, PI. XXX., fig. 14). 



Genus Tintinnidium. 



Tintinnidium fiuviatile, Stein, var. emarginatum, var. nov. 

 Plate III., fig. 16, a, b, c, d. 



Animalcules excreting a cylindrical, gelatinous tube or lorica, 

 attached by its base to aquatic plants, or rarely to stems of 

 Zoothamnium or Epistylis ; at times free-swimming. Lorica 

 transparent, but usually covered by a quantity of vegetable or 

 other particles adhering to it. Animalcule white, campanulate, 

 attached to the base of the tube by a slender, highly-retractile 

 pedicle ; when fully extended reaching only to the mouth of 

 the tube, or projecting very slightly beyond it. Peristome 

 occupying almost all the width of the tube, the edge not at all, 

 or very slightly, recurved. Peristome-edge on one side entire, 

 bearing a number of long, thick, cirrose cilia ; the other side 

 bearing very few, shorter, cirrose cilia, and apparently cleft into 

 three divisions, the middle one bearing no cilia ; this median 

 division pulsates regularly up and down as on a hinge. On the 

 anterior portion of the body, below the peristome-edge, are a 

 few short, straight, fine setae placed at right angles to the 

 margin ; possibly, if the tube permitted full examination, these 

 might be seen to extend to the pedicle. Contractile vesicle 

 single, spherical, situated a little below the peristome-edge. 

 Nucleus not observed. 



Animalcules may frequently be seen unattached within their 

 tubes, as in fig. 16, a (the right-hand figure) ; they then escape 

 at pleasure from the tube and become free-swimming, in the 

 form shown in fig. 16, c, when they may easily be mistaken for 

 free Vorticella. In the end-view of such a form the adoral cilia 

 are seen to be disposed spirally (fig .16, d) as in Strombidium, 

 and the motion is rapidly rolling. 



Food-particles appear to be taken in at the two small clefts 

 on one side of the peristome-edge, shown in fig. 16, b, and the 

 pulsating middle division seems to act after the manner of a 

 valve. 



The structural details above given are not easily observed on 

 account of the covering of foreign particles on the lorica, and 

 the fact that the animalcule scarcely protrudes beyond the 

 orifice of the tube. Sometimes, however, a lorica less thickly 

 coated permits fairly close observation. 



