256 MONADS CHAP. 



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 by zoologists and by 

 botanists. 



Another mode of nutrition occurs in certain organisms 

 which must now be referred to very briefly. 



FIG. 70. A Monad (Hcteromita rostrata), showing nucleus (nit), contractile 

 vacuole (c. vac}, and two flagella (y? 1 , jff 2 ). From Parker's Biology, after 

 Dallinger. 



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 (pp. n, 152, and 

 237) 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, the form represented in Fig. 70 (Heteromita) 

 being only about T ^y- mm. (^o\r <r i ncn ) m length. Like 

 Sphserella, 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 



