178 CHARACTERS OF ANIMALS AND PLANTS 



either from simple salts or from proteids, and the process of 

 nutrition is one of oxidation. There is no special excretory 

 organ, and, except in the case of certain reproductive bodies 

 there is no locomotion as a rule. 



Let us now apply these definitions to the simple forms 

 described in the first eight lessons, and see how far they 

 will help us in placing those organisms in one or other of 

 the two " kingdoms " into which living things are divided. 



Amoeba has a cell-wall, probably nitrogenous, in the 

 resting condition : it ingests solid proteids, its nutrition being 

 therefore holozoic : it has a contractile vacuole : and it 

 performs amoeboid movements. It may therefore be safely 

 considered as an animal. 



Haematococcus has a cellulose wall : it contains chloro- 

 phyll and its nutrition is purely holophytic : a contractile 

 vacuole is present in H. lacustris but absent in H. pluvialis : 

 and its movements are ciliary. 



Euglena has a cellulose wall in the encysted state : in 

 virtue of its chlorophyll it is nourished by the absorption of 

 carbon dioxide and mineral salts, but it can also ingest solid 

 food through a special mouth and gullet : it has a contractile 

 vacuole, and performs both euglenoid and ciliary move- 

 ments. 



In both these organisms we evidently have conflicting 

 characters : the cellulose wall and holophytic nutrition 

 would place them both among plants, while from the con- 

 tractile vacuole and active movements of both genera and 

 from the holozoic nutrition of Euglena we should group 

 them with animals. That the difficulty is by no means 

 easily overcome may be seen from the fact that both genera 

 are claimed at the present day both by zoologists and by 



