250 STILL AND MOTILE STATES OF PROTOCOCCUS. 



tion of a new brood, and so on. — The activity of Motion and the 

 activity of Multiplication seem to stand, in some degree, in a rela- 

 tion of reciprocity to each other ; for the self-dividing process 

 takes-place with greater rapidity in the ' still ' cells, than it does 

 in the 'motile.' 



192. What are the precise conditions which determine the 

 transition between the 'still' and 'motile' states, cannot yet be 

 precisely stated ; but the influence of certain agencies can be pre- 

 dicted with tolerable certainty. Thus it is only necessary to pour 

 the water containing these organisms from a smaller and deeper 

 into a larger and shallower vessel, at once to determine segmenta- 

 tion in numerous cells, — a phenomenon which is observable also in 

 many other Protophytes. The ' motile ' cells seem to be favour- 

 ably affected by Light, for they collect themselves at the surface of 

 the water and at the edges of the vessel ; but when they are about 

 to undergo segmentation, or to pass into the ' still ' condition, they 

 sink to the bottom of the vessel, or retreat to that part of it in 

 which they are least subjected to light. When kept in the dark, 

 the 'motile' cells undergo a great diminution of their chlorophyll, 

 which becomes very pale, and is diffused, instead of forming definite 

 granules ; they continue their movement, however, uninterruptedly, 

 without either sinking to the bottom, or passing into the still 

 form, or undergoing segmentation. A moderate warmth, particu- 

 larly that of the vernal sun, is favourable to the development of 

 the ' motile ' cells ; but a temperature of excessive elevation 

 prevents it. Rapid evaporation of the water in which the 'motile' 

 forms may be contained, kills them at once ; but a more gradual 

 loss, such as takes-place in deep glasses, causes them merely to 

 pass into the 'still' form ; and in this condition, — especially when 

 they have assumed a red hue, — they may be completely dried-up, 

 and may remain in a state of dormant vitality for many years. It is 

 in this state that they are wafted-about in atmospheric currents, 

 and that, being brought-down by the rain into pools, cisterns, &c, 

 they may present themselves where none had been previously 

 known to exist ; and there, under favourable circumstances, they 

 may undergo a very rapid multiplication, and may maintain them- 

 selves until the water is dried-up, or some other change occurs 

 which is incompatible with the continuance of their vital activity. 

 They then very commonly become red throughout, the red colour- 

 ing-substance extending itself from the centre towards the circum- 

 ference, and assuming an appearance like that of oil -drops; and 

 these red cells, acquiring thick cell-walls and a mucous envelope, 

 float in flocculent aggregations on the surface of the water. This 

 state seems to correspond with the 'winter spores' of other Proto- 

 phytes ; and it may continue until warmth, air, and moisture 

 cause the development of the red cells into the ordinary ' still' 

 cells, green matter being gradually produced, until the red sub- 

 stance forms only the central part of the endochroine. After this 



