THE FLAGELLATA 203 



not known, but it does not give sthe reactions of cellulose. 

 There is no mouth, but two contractile vacuoles may be seen 

 close to the bases of the flagella. A nucleus is placed near 

 the hind end of the body, and generally a small stigma or 

 nodule of haematochrome may be distinguished in the anterior 

 half of the body. Though Polytoma has no chromatophors, 

 is colourless and devoid of chlorophyll, it has the power, 

 usually possessed only by organisms which contain chlorophyll, 

 of storing up amylum in its body. Close observation shows that 

 the posterior half of every well-nourished individual is filled with 

 small granules, which, when treated with iodine, give the charac- 

 teristic reactions of starch. If a Polytoma is starved by being 

 transferred to a liquid devoid of nutrient organic matter, the 

 starch granules gradually diminish in size, and finally they dis- 

 appear and the animal dies. The exact mode of formation of 

 these starch granules is not understood. They are not ingested, 

 for Polytoma has no mouth, and has never been seen to ingest 

 solid particles, nor are any foreign matters excepting these 

 starch granules to be seen in its protoplasm. Its nutrition must 

 be described as saprophytic, for it lives immersed in a nutrient 

 fluid, and imbibes it by the whole surface of its body. It 

 evidently does not get its carbon from carbon dioxide, for, as 

 we have just seen, it becomes enfeebled and dies if it is taken 

 from the nutrient solutions in which it lives, and therefore it 

 must form starch in some other manner than its chlorophyll- 

 containing relatives. Now, in the higher animals a form of 

 amylum, known as glycogen or animal starch, is found in some 

 abundance in the liver and in muscle. Numerous experiments 

 have shown that glycogen is formed, in the dog for instance, 

 when the animal is kept on an exclusively proteid diet, and it 

 is therefore proved that starch may be formed by the activity 

 of living tissue from proteid material. It cannot be doubted 

 that the protoplasm of Polytoma has this same power of 

 converting the albuminous substances which it absorbs from 

 organic solutions into starch. Attention should be paid to 

 the existence of starch in Polytoma wuella, for it is sometimes 

 incorrectly said that organisms devoid of chlorophyll never 

 contain starch. Polytoma reproduces itself by a process of 

 continued division within the cell envelope, either in the 

 free swimming or in a resting condition. The act of division 

 may nearly always be seen in individuals which are kept 



