INVERTEBRATA. 411 



or similar to that of typical animals or animal cells, as, for 

 example, Amoeba or Paramecium. The presence of chloro- 

 phyll, and experiments showing that C0 2 is absorbed and 

 O evolved by Euglena when exposed to light, indicate that 

 holophytic nutrition occurs, or that the organisms are able 

 to live like green plants. But experiment shows that 

 when Euglena is cultivated with only inorganic materials 

 in solution and exposed to light the cells do not divide 

 rapidly and do not appear vigorous. On the other hand, 

 when the organisms are kept in the dark in solutions con- 

 taining decomposing organic compounds including carbo- 

 hydrates and nitrogenous compounds in solution they 

 thrive and multiply, but lose their chlorophyll. This 

 shows that they can nourish themselves saprophytically, 

 like fungi. The normal condition appears to be a com- 

 bination of these two forms of nutrition, the holophytic 

 and the saprophytic ; hence the fact that in the natural 

 state Euglena occurs chiefly in waters containing organic 

 matter in considerable quantity. But, like fungi, they 

 absorb organic compounds in solution and do not ingest 

 them as solid particles. 



10. Paramylum. This substance has the same chem- 

 ical composition as starch, C 6 H 10 5 , but differs from it in 

 its reactions. It is not coloured blue by iodine ; it is not 

 affected by organic acids or by alcohol or ether. Potash 

 in strong solution dissolves it rapidly, and sulphuric acid 

 more slowly. Paramylum is in Euglena a store of carbo- 

 hydrate food, but it appears to be formed not only in the 

 chloroplasts, as in plants, but also in the cytoplasm inde- 

 pendently of the chloroplasts. The latter process is due 

 to the saprophytic mode of nutrition, the former to the 

 holophytic. 



11. Nuclear Division. We have seen that the nucleus 

 of Euglena in division goes through certain changes which 

 have a distant resemblance to the mitosis of the cells of 

 Metazoa. According to Keulen the nucleo-centrosome is 

 surrounded by somewhat elongated rod-like chromosomes 

 which during division arrange themselves parallel to the 



