Prof. Ilciifrcv on the Ccll-cuntmts o/" Closterium. 421 



fino graiuik's, apjH'armg; like black specks with the highest 

 powers ; besides tiiese point-like granules, the liquid contains a 

 variable but not great number of somewhat larger (perhaps 

 starch-) granules, many of which are often found in the clear 

 spaces at the ends of the cell. The said clear spaces arc vacuoles 

 in the finely granular protoplasm lying between the green matter 

 and the cell-wall. These vacuoles do not exhibit any rhythmi- 

 cal contraction and expansion, but they alter in form, and 

 even move about in the limited space which they occupy, in 

 obedience to the impulse of the currents of circulation. Nor- 

 mally, or when the circulation is in equilibrium, the clear spaces 

 are round, and in the middle of the bluntly triangular space at 

 the end of the cell. When the currents of circulation are of 

 different force on the two sides, the vacuole is often driven to 

 one or other side ; and I have even seen it driven over so as to 

 be |)artially insinuated into the space at the side of the green 

 matter, as if it were going to travel down in the submarginal 

 space, with the circulating fluids, towards the thicker part of the 

 cell ; in all cases, however, it soon returned to its place in the 

 centie of the end- space. By pressure, driving the green endo- 

 chrome towards the end of the cell, the vacuole was obliterated. 

 The presence of the granules, exhibiting what has been called 

 a " swarming" movement in the vacuoles, is, as we may term it, 

 accidental. They do not always exist there, and are evidently 

 the same larger granules which are found floating about irregu- 

 larly in the circulating protoplasm. When brought iip to the 

 ends, they readily pass into the vacuole ; and the vacuole being 

 kept in movement by the eddies of surrounding currents, the 

 contained granules are 'rattled' about as in a box; and their 

 movements being dependent upon external influence, they can- 

 not get out of their prison, — hence their accumulation in the 

 vacuolar spaces. In the submarginal clear region these same 

 granules are seen to be moved, as it appears, irregularly, 

 sometimes forwards, sometimes backwards, sometimes inwards, 

 and often with a tremulous oscillation, like molecular motion. 

 This is attributable to their being taken up and let go by op- 

 posing currents of the circulating substance, just as the globules 

 in the central space of the Chura-CiA\ are moved onwards by the 

 circulating protoplasm when they come in contact with it. 



In the last place, and as the matter of most importance, comes 

 the question of the circulation itself, rendered manifest by the 

 rapid flowing motion of the point-like granules in the colourless 

 submarginal protoplasm. Every one has noticed that the cur- 

 rents flow in various directions, and that the currents often flow 

 towards the end of tlie cell on both edges, so that we have not a 

 true "rotation," as in I'allisneria. It may be observed, more- 



