2S6 MONADS CHAP. 



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 diflficulty 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 

 botanists. 



Another mode of nutrition occurs in certain organisms 

 which must now be referred to very briefly. 



When animal or vegetable matter is placed in water and 

 allowed to stand at the ordinary temperature, the well-known 

 process of decomposition or putrefaction (p. ii and 152) 

 sooner or later sets in, the water becoming turbid and 

 acquiring a bad smell. A drop of it examined under the 

 microscope is then found to teem with very minute unicellular 

 organisms, some of which are known as Monads, much smaller 

 than Euglena. Like Haematococcus, the Monad swims about 

 by means of two flagella, but it contains no chlorophyll. The 

 putrefying infusion in which it lives contains proteids in 

 solution, in part split up by the process of decomposition into 

 simpler compounds, some of which are diffusible. As the 

 Monad contains no chlorophyll, its nutrition is evidently not 

 holophytic, and, apart from the fact that it possesses neither 

 mouth nor pseudopods, observation seems to show pretty 

 conclusively that it is not holozoic. 



There remains only one way in which nutrition can take 

 place, namely, by absorption of the proteids and other 

 nutrient substances in the solution : the Monad may be 

 said to live immersed in an immense cauldron of broth which 

 it is for ever imbibing, not by its mouth, for it has none, but 

 by the whole surface of its body. This is the saprophytic 



