244 lI.EMATOCOCCUS chap 



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

 something like a delicate haze round the red or green bod)', 

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

 globular shell (a, c.7t'), composed of some colourless trans- 

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

 from the body, to which it is connected b)' very delicate 

 radiating strands of protoplasm. It is perforated l:)y two 

 extremely minute apertures for the passage of the flagella. 

 Obviously we may consider this shell as a cyst or cc//- 

 ivall, differing from that of an encysted Amceba (Fig. 67, 11) 

 in not being in close contact with the protoplasm. 



A more important difference, however, lies in its chemical 

 composition. 'l"he cyst or cell-wall of Amceba, as stated in 

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

 that of Haamatococcus, 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 CgHjuO-,. 

 Many vegetable substances, ^uch as cotton, consist of 

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

 pound. Cellulose is stained )ellow by iodine, but iodine 

 and sulphuric acid together turn it blue, and a similar 

 (■(jlour is produced by a solution of iodine and potassium 

 iodide in /.inc chloride known as Schul/,c's solution. These 

 tests are quite easily applied to H;eniatococcus : 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 Hajmatococcus some- 

 times assume an arn(xboid form. In any case, afier 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 (k'ig. 68, n), thus becoming encysted. So 



