SOME MOOT POINTS IN NATURAL HISTORY. 245 



as the scientific appellation of this ill-defined border-land of 

 modern natural history. But, as has well been remarked, 

 the recognition of this intermediate ground simply " doubles 

 the difficulty which before was single." In other words, the 

 task of taking the scientific census of " no man's land " 

 would prove a difficulty of no ordinary kind, in addition to 

 that already imposed upon the naturalist of attempting to 

 simply distinguish the members of the animal series, and 

 to determine the definite characteristics of the plant. 



One or two examples, however, will illustrate more 

 effectually than many precepts, the nature and extent of the 

 difficulties which meet the biologist in his researches into the 

 life-history of lower organisms. If we take a handful of 

 chopped hay, pour boiling water thereupon, and, in short, 

 infuse the hay after the fashion of the " cup that cheers," 

 and microscopically examine such an infusion some days 

 thereafter, when the mixture exhibits signs of turbidity and 

 of commencing decomposition, we find therein a large 

 number of minute living organisms, amongst which the 

 active little specks, known generally under the name of 

 Monads, form prominent objects. The monads consist each 

 of a microscopic particle of living matter, which exhibits 

 little or no traces of the structures we are accustomed to 

 associate with animal or plant life in its higher phases of 

 development. As regards size, these members of the teem- 

 ing population of our hay-infusion do not exceed the ^ooth 

 part of an inch in length. The body in the common species 

 is pear-shaped, and to the slender extremity of the body one 

 or more exceedingly delicate filaments, named cilia, are seen 

 to be attached. By the aid of these organs the little monads 

 propel themselves through the miniature sea in which they 

 live, and very swiftly indeed do these living specks contrive 

 to move about ; the spectacle, familiar to every microscopist, 

 forcibly reminding the observer of the jostling crowds and 

 traffic in the thoroughfares of a great city. A careful study 

 of the monads reveals the interesting, but in one sense pain- 

 ful, fact, that we are utterly unable to say what they are. 



