574 VISIBLE CONSTRUCTIVE ACTIVITY IN PROTOPLASM. 



masses. Even when the wall remains, and is not ruptured nor disintegrated, it is 

 separated from the protoplasmic masses by the new cell-walls, with which these 

 have meanwhile surrounded themselves. For every species of plant the number, 

 size, and shape of the bodies arising in the interior of a cell by division are 

 quite definite, though they vary from species to species. In the cell-chambers 

 of some species several thousand minute protoplasmic bodies arise. In others, 

 again, the number is very limited. Frequently, indeed, the protoplasm only splits 

 up into two similar halves. If the number is large, the individual masses are 

 exceedingly small, and can only be recognized when very greatly magnified. If 

 the number is limited, the divided portions are comparatively large. The shape 

 of the structures is exceedingly various. Some are spherical, elliptical, or pear- 

 shaped; others elongated, fusiform, filamentous, or spatulate; some are straight, 

 others are spirally twisted, and many are drawn out into a thread ; others are 

 provided over the whole surface with short cilia, others again with a crown of 

 cilia at a particular spot, or with only a single pair of long cilia. The illustration 

 on p. 29 represents the most widely dififering forms, without, however, exhausting 

 the wealth of configuration. In the majority of cases the small bodies exhibit 

 active movements, and that even within the cell-covering which surrounds the 

 dividing protoplasm ; but sooner or later they come to rest, and then assume another 

 shape, or fuse with another protoplasmic body. 



With regard to the further changes experienced by the bodies formed by 

 division, many events may be distinguished. In one, the cell in which the division 

 of the protoplasm has taken place opens, the bodies formed glide out separately 

 and swarm in the surrounding fluid. Often they are concerned in fertilization, and 

 fuse with other protoplasmic bodies in a manner to be described later in detail. If 

 not, they surround themselves with a cell-wall, but do not adhere together, or 

 develop into a cell-colony. 



In the Water-net {Hydrodictyon), described on p. 36 (cf. fig. 197, vol. II.), the 

 parietal protoplasm of a cell divides up into 7000-20,000 minute clumps which 

 exhibit the so-called swarming movement. At first a definite aim cannot be 

 assigned to these movements, but after a short time the particles appear arranged 

 very regularly in a net with hexagonal meshes. They assume the form of short 

 rods, each of which joins at its poles with two others, being cemented to them 

 by excreted cellulose. Instead of a protoplasmic parietal layer in the cell in 

 question a miniature water-net is now seen to have arisen. This becomes free 

 with the disintegration of the parent-cell ; its cells grow and increase in all 

 directions without, however, altering the shape once assumed. The process which 

 is observed in Pediastrum (fig. 197, vol. II.), a very small water plant allied to the 

 water-net, is very much the same. Here also the protoplasm of a cell which has 

 isolated itself from the others divides up into small clumps which round themselves 

 ofi", and swarm about for a short time. Gradually they come to rest, assume an 

 angular form, and arrange themselves so as to form two concentric rings in one 

 plane. Where they come into contact with each other, they excrete cellulose and 



