244 H^MATOCOCCUS chap 



reference has yet been made. This appears at the first view 

 something Hke a delicate haze round the red or green body, 

 but by careful focussing is seen to be really an extremely thin 

 globular shell (a, c.w), composed of some colourless trans- 

 parent material, and separated, by a space containing water, 

 from the body, to which it is connected by very delicate 

 radiating strands of protoplasm. It is perforated by two 

 extremely minute apertures for the passage of the flagella. 

 Obviously we may consider this shell as a cyst or cell- 

 wall, differing from that of an encysted Amoeba (Fig. 67, d) 

 in not being in close contact with the protoplasm. 



A more important difference, however, lies in its chemical 

 composition. The cyst or cell-wall of Amoeba, as stated in 

 the preceding chapter (p. 232), is very probably nitrogenous ; 

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

 carbohydrate called cellulose, allied in composition to starch, 

 sugar, and gum, and, like starch, having the formula CjHjdOj. 

 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 Hsematococcus : 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 Hjematococcus some- 

 times assume an amceboid form. In any case, after lead- 

 ing an active existence for a longer or shorter time, it 

 comes to rest, loses its flagella, and forms a thick cell- 

 wall of cellulose (Fig. 68, b), thus becoming encysted. So 



