120 PROCEEDINGS OF THE ACADEMY OF [PaRT I 



our Bicoeca exilis; but the special shape of the capsule, as also the 

 very exceptional length of the flagellum, seem to point to a special 

 organism, which has not yet been described. 



Histiona campanula sp. n. Plate VI, figs. 14-19. 



During the autumn of 1917, I found in a pond at Pinchat, a small 

 Flagellate which seems to belong to Histiona, a genus itself very 

 little known. It was most generally found fixed on the threads of 

 a certain Zygnema, very often forming long colonies of indi- 

 viduals, standing next to each other along the mucilaginous sheath 

 of the alga. 



The protoplasmic body, very clear and delicate, occupies less 

 than half of the capsule (Plate VI, fig. 14), which latter is itself 

 so thin and transparent that its structure is not determined without 

 some difficulty. It may be compared to an inverted bell, broadly 

 open upwards, and whose closed end would be stretched on one 

 side, so as to make a horn-like prolongation; and owing to this 

 special form the little case, which rests with its posterior point just 

 on the surface of the mucilaginous sheath, appears bent down like a 

 small flower {Campanula) on its stalk, the concave side of the cap- 

 sule being towards the Zygnema (Plate VI, fig. 14). The little 

 capsule is at the same time laterally compressed, and seen from 

 behind looks somewhat hke a sugar-loaf (Plate VI, fig. 15). The 

 capsule is provided with a pedicle, thin and colorless, which goes 

 right through the jelly and joins the surface of the cellulose mem- 

 brane of the Zygnema, where it is most generally seen to attach by 

 means of a shining little cushion. The pedicle, we must observe, 

 is not a true pedicle in fact, but is rather a protoplasmic thread 

 more solidly affixing the cell to the substratum; the jelly alone 

 . would not allow of a sufficient hold; and, by the way, we must add 

 that the mucilaginous layer being generally perfectly invisible, the 

 capsule seems to be provided with a stalk, as for the length of this 

 stalk, it is of course equal to the thickness of the mucilaginous layer, 

 about 13[JL or sometimes a little more or less. The protoplasmic 

 body, which appears as if suspended inside the capsule without 

 anything to keep it in place, is also very individual in its appear- 

 ance: rounded behind, cup-shaped anteriorly, it is drawn up on 

 one of its borders (always the same, that which is in contact with 

 the convex face of the shell) into a long trunk-like appendage, which 

 passes beyond the capsule and protrudes into the surrounding 

 liquid. From the tip of that peculiar appendage stretch right and 

 left two thin and broad protoplasmic curtains, which, passing over 

 the intervening space join at last the opposite border of the cell. 

 In fact, these curtains, or veils, may be considered as representing 

 the extreme borders of the cup-shaped body, which have grown 

 very thin and transparent. One of these veils, moreover, is much 

 more developed than the other, and about the middle of its course 



