28 H^MATOCOCCUS 



that of Haematococcus, on the other hand, is formed of a 

 carbohydrate called cellulose, allied in composition to 

 starch, sugar, and gum, and having the formula C 6 H 10 O 5 . 

 Many vegetable substances, such as cotton, consist of 

 cellulose, and wood is a modification of the same com- 

 pound. Cellulose is stained yellow by iodine, but iodine 

 and sulphuric acid together turn it blue, and a similar 

 colour is produced by a solution of iodine and potassium 

 iodide in zinc chloride known as Schulze's solution. These 

 tests are quite easily applied to Haematococcus : the proto- 

 plasm stains a deep yellowish-brown, around which is seen 

 a sort of blue cloud due to the stained and partly-dissolved 

 cell-wall. 



It has been stated that in stagnant water in which it has 

 been cultivated for a length of time Haematococcus some- 

 times assumes an amoeboid form. In any case, after leading 

 an active existence for a longer or shorter time it comes to 

 rest, loses its flagella, and throws around itself a thick cell- 

 wall of cellulose (Fig. 3, B), thus becoming encysted. So 

 that, as in Amoeba, there is an alternation of an active 

 or motile with a stationary or resting condition. 



In the matter of nutrition the differences between Haema- 

 tococcus and Amoeba are very marked and indeed funda- 

 mental. As we have seen, Hsematococcus has no pseudopods, 

 and therefore cannot take in solid food after the manner 

 of Amoeba : moreover, even in its active condition it is 

 usually surrounded by an imperforate cell-wall, which of 

 course quite precludes the possibility of ingestion. As a 

 matter of observation, also, however long it is watched it is 

 never seen to feed in the ordinary sense of the word. 

 Nevertheless, it must take in food in some way or other, or 

 the oxidation of its protoplasm would soon bring it to an end. 



