74 ON THE DESMIDIACE.E. 



active life. Streams of protoplasm appear to be constantly passing 

 to and fro between the nucleus and the ends of the cell along the 

 outer zone, and granules can be always seen passing backwards and 

 forwards with an unsteady motion. 



When streams of protoplasm are setting very actively from the 

 centre towards one end, there will often be an accumulation of the 

 protoplasm there, and a consequent decided lessening in the size of 

 the vacuole, which will again expand as the return currents arouse 

 themselves. Within the vacuoles are seen more or less numerous 

 smaller or larger granules in active, busy motion, swarming over 

 and about one another with an unsteady hurrying to and fro. 



A form of motion, similar to this in appearance, but probably of 

 different significance, is seen in most Desinids when in an unhealthy, 

 feeble condition. I have seen it most marked in Cosmarium 

 margaritaceum. In such fronds the endochrome has lost its deep 

 green colour, and become shrunken, and lying within it is a great 

 space containing myriads of minute, blackish particles swarming 

 about actively. This peculiar state and appearance is by no means 

 confined to the Desmids, for I have seen it very highly developed 

 both in species of Spirogyra and CEdogonium. It appears to be 

 connected with decay. Is it possible that these minute particles 

 are foreign to the plant, vibrionic in nature ? 



In regard to the nature of the movements seen within a healthy 

 Desmid, some have viewed them as exceedingly mysterious, the 

 result of the presence of cilia, &c; but these views have been so 

 thoroughly exploded that it is scarcely necessary even to mention 

 them here. The movements are, in truth, precisely parallel to the 

 so-called cyclosis of the higher plants. Protoplasmic germinal 

 matter, wherever it exists, be it in animal or vegetable, has, as one 

 of its distinguishing characters, the power of active, spontaneous, 

 apparently causeless movements, and it is simply the carrying out 

 of this power or attribute which has attracted so much attention in 

 the Desmids, because it is in them so readily seen. 



There are, in this family, two distinct methods in which the 

 species are multiplied, one with, the other without, the intervention 

 of anything like sexuality. The non- sexual method of increase is 

 really a modification of an ordinary vegetative process, a peculiar 

 cell multiplication by division. In such fronds as those of the genus 

 Cosmarium, which are composed of two evident halves connected 

 by a longer or shorter isthmus, the first step in the process is an 

 elongation of this neck. In a very short time there appears around 

 the centre of this a constriction, and, I believe, an actual rupture 

 of the outer coat. By this time a new wall has formed inside each 

 half of the isthmus, and stretches also across its cavity, forming, 

 with its fellow, a double partition wall, separating the two halves 

 of the old frond. Rapid growth of the newly formed parts now 

 takes place, the central ends become more and more bulging as 

 they enlarge, and in a little time, two miniature lobules have 



