H/EMATOCOCCUS 29 



When a dried -up sample of Htematococcus is supplied with 

 fresh rain-water and placed in the sunlight it undergoes a 

 remarkable change. The protoplasmic body within the cell-wall 

 undergoes division, first into two and then into four parts 

 (Fig. 5, B). This is effected by a process of simple fission exactly 

 comparable to that which we have already described in the case 

 of Amoeba. The four parts or daughter cells (sometimes called 

 zoospores) are for a short time kept together within the old cell- 

 wall, but presently this ruptures and they escape into the 

 surrounding water. 



It will now be seen that these so-called zoospores differ greatly 

 in structure from the resting Haematococcus. Instead of being 

 spherical they are more or less oval or pear-shaped in outline 

 (Fig. 5, C). Each has secreted a new cellulose wall of its own 

 (c.w.), but this is separated from the main protoplasmic body by 

 a considerable space, or vacuole, filled with water (vac.), across 

 which stretch delicate threads of colourless protoplasm, which 

 keep the protoplasmic body in position. The main mass of 

 protoplasm is coloured red or green, as before, and contains the 

 nucleus (??%.). At one end it is drawn out into a kind of beak, 

 from which two very long and slender threads of colourless 

 protoplasm (ft.) pass outwards, through minute apertures in the 

 cellulose wall, into the surrounding water. Owing to their 

 whip-like form and characteristic lashing movements, these are 

 termed nagella. 



It is by the very rapid movements of the nagella that the 

 locomotion of the active Hsematococcus is effected. They are 

 carried in front, and the body of the organism is pulled through 

 the water by their action much as a boat is pulled by a pair of 

 sculls, at a rate which, though very slow when judged by our 

 own standards, appears very rapid when considered in relation to 

 the minute size of the organism. The movements of the nagella 

 are somewhat complex and of an undulatory kind. They appear 

 to be entirely automatic, but it seems probable that they must 

 be performed in response to stimuli which we are unable to 

 recognize. The nagella are much more definite and highly 

 specialized structures than the pseudopodia of an Amoeba. Like 

 the latter, hawever, they owe their value as organs of locomo- 

 tion to that inherent power of contraction which is one of the 

 most characteristic features of living protoplasm. It is probable 

 that each really consists of several very slender filaments, lying 



