140 THE MICROSCOPIST. 



Sometimes a conjugation or fusion of cells occurs, and the 

 product is a spore or primordial cell of a new generation 

 (Plate IX, Fig. 110). During conjugation oil is produced 

 in the cells, and the chlorophyll disappears or becomes 

 brown, and when the spore vegetates, the oil disappears 

 and green granular matter takes its place. This is analo- 

 gous to the transformation of starch into oil in the seeds 

 of the higher plants. 



Most of the lower forms of vegetable life pass through 

 what is called the motile condition, which depends on the 

 extension of the bioplasm into thread-like filaments, whose 

 contractions serve to move the cell through the water. 

 Many of these forms were formerly mistaken for animal- 

 cules, and the transformation of a portion of green chlo- 

 rophyll into the red form was represented as an eye. The 

 multiplication of the "still" cells is by self-division, as in 

 Palmoglcea, but after this has been repeated about four 

 times, the new cells become furnished with cilia and pass 

 into the "motile" condition, and their multiplication goes 

 on in different ways, as by binary or quaternary segmen- 

 tation, or the formation of a compound, mulberry-like 

 mass, the ciliated individual cells of which, becoming free, 

 rank as zoospores (Plate X, Fig. 111). 



The Volvox is a beautiful example of the composite 

 motile form of elementary vegetation. It is found in 

 fresh water, and consists of a hollow pellucid sphere, 

 studded with green spots, connected together often by 

 green threads. Each of these spots has two cilia, whose 

 motions produce a rolling movement of the entire mass. 

 Within the sphere there are usually from two to twenty 

 smaller globes, which are set free by the bursting of the 

 original envelope. Sometimes one of the masses of endo- 

 chrome enlarges, but instead of undergoing subdivision 

 becomes a moving mass of bioplasm, which cannot be dis- 

 tinguished from a true Amoeba or primitive animal cell. 



The Desmidiacece are a family of minute green plants 



