296 '^ The Microscope. 



That these germs teeming in the hay infusion are alive, no one 

 questions. But why relegate them to the animal kingdom rather 

 than to the vegetable ? It is no longer difficult to. refer any one of 

 the complex or multicellular beings to one or the other of these two 

 parallel series; there are no longer serious differences of opinion 

 concerning such among the learned; but to satisfactorily divide 

 unicellular forms, placing this among protozoa, and that one among 

 protophyta is another matter, one which the present state of knowl- 

 edge does not enable men to agree upon. The distinguished 

 biologist, Ernst Haeckel, has proposed to remove the difficulty by 

 establishing a third kingdom, protista. To this many doubtful 

 species, and many that are not so, have been assigned by him. He 

 has distinguished followers. Still, to many the proposition seems 

 to increase rather than diminish the perplexity, for now we have 

 two questions instead of one to contend with, viz: To separate pro- 

 tista from animals on the one hand, and second, from plants on the 

 other. Again, if I understand aright the tendency of modern 

 research concerning this matter, the number of forms which can 

 not be assigned with good reason to either the vegetable or the 

 animal series, is constantly growing smaller. In short, it seems 

 to me, protista is gradually tapering to a point, as knowledge 

 advances, and at no very distant period there will be no use for it 

 in the sense it was first proposed and limited. 



I prefer to keep to the old lines and regard these lowest beings 

 as either plants or animals, according to the best light we have. 

 That mistakes will be made for subsequent study to correct must 

 be expected. But that there will be more than by any yet proposed 

 arrangement, I cannot believe. 



This little swimmer from the infusion is known in the system 

 as heteromita. Why is heteromita an animal? 1. It feeds on 

 organic matter of the infusion in which it flourishes. Since it con- 

 tains in its body none of that peculiar substance, chlorophyl, which 

 enables protoplasm to create its own food out of the simple sub- 

 stances, Hj O, CO2 and N Ha in the presence of sunlight. On the 

 other hand, it must borrow its substance and energy from other and 

 independent sources. 



At this point two questions naturally arise which are in the 

 nature of exceptions: 1. There are well-known and undisputed 

 plants with the habits of animals, i. e., they feed on organic food 

 prepared outside themselves. Whilst it is a rule that animals feed 

 as our infusorian does, upon the substance prepared ultimately by 



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