USE OF THE MICROSCOPE IN ZOOLOGY. 39 



all intents and purposes a fungus, and formerly was 

 always regarded as such ; but the remarkable in- 

 vestigations of De Bary* have shown that in another 

 condition the ^Ethalium is an actively locomotive 

 creature, and takes in solid matters, upon which 

 apparently it feeds, thus exhibiting the most charac- 

 teristic feature of animality. Is this a plant, or is it 

 an animal ? Is it both ; is it neither ? Some decide 

 in favour of the last supposition, and establish an 

 intermediate kingdom, a sort of biological No Man's 

 Land, for all these questionable forms. But as it is 

 admittedly impossible to draw any distinct ' boundary 

 line between this No Man's Land and the vegetable 

 world on the one hand, or the animal on the other, it 

 appears to be that this proceeding merely doubles the 

 difficulty, which before was single, t 



Notwithstanding, however, the great difficulty, if 

 not impossibility, of drawing a distinction between 

 some of the lowest forms of the animal and vegetable 

 kingdoms, as a general rule the boundaries are suffi- 

 ciently distinct. I have called your attention to the 

 remarks of Professor Huxley on this subject, in order 

 that you may see what great problems the microscope 

 helps to solve. I will now direct you to a considera- 

 tion of some of the minute forms of undoubted animal 

 life which every pond or ditch contains in endless 

 variety and profusion. Of so-called monads extremely 

 minute organisms found in water containing decom- 

 posed vegetable or animal matter, several supposed 

 species of which have been described I need say but 

 little. There can be no doubt, notwithstanding the 

 opinion of Ehrenberg, that the Monadina family con- 



* "Die Mycetozoen." Leipzig, 1864; also an abstract in Hoff- 

 meister's "New System of Botany." 



t "Oft the Physical Basis of Life." Fortnightly Review, Feb., 

 1869. 



