CnLOllOPUYLL-CONTAINING INFUSOPxIA. 177 



Other forms are omnivorous (e.g., Stentor^ Bursarla)^ feeding 

 both on vegetable and on animal food. Others still are car- 

 nivorous and lead a predatory life, often attacking herljivorous 

 forms much larger than themselves, precisely as is the case with 

 carnivores among the mammalia. Thus the unicellular \v()rl<l 

 reproduces in miniature the essential biological relations of 

 higher types. 



It is a remarkable fact that some species of Infusoria (e.g., 

 Parainoacitiin hursaria^ Yorticella viridis) contain numerous 

 chlorophyll-bodies embedded in the entoj^lasm. Much discus- 

 sion has arisen as to whether these bodies are to be regarded as 

 an integral part of the animal, i.e., differentiated out of its own 

 protoplasm, or as minute plants living ' ' symbiotically " (i.e. as 

 mess-mates) within the animal. In the forme:* case (which is 

 the most probable) the animal w^ould to a certain extent be 

 nourished after the fashion of a green plant (cf. p. lis). 



It will now be clear to any one wdio has carefully considered 

 the phenomena described in the foregoing pages that the uni- 

 cellular animals are "organisms" by right, and not merely by 

 courtesy. In some of the Infusoria, for example, differentia- 

 tion within the single cell may go so far as to give rise to primi- 

 tive sense-organs (as in the case of the eye-spot of Euglena) ; a 

 rudimentary oesophagus and definite mouth (as in Parammciiuri 

 and Yorticella) ; organs of locomotion (cilia, flagelld) ; organs 

 of excretion (contractile vacuoles) etc. , etc. 



