26 Transactions of the American Institute. 



multiplication by subdivision, or fissuration, of a few individuals of a 

 single species oi jparamecium^ computed that in a month 268,000,000 

 might proceed from a single one. 



But another curious discovery has been brought to light by the 

 microscope among these humble forms of life. The unicellular plants 

 are generally, at least at some period of their existence, free ; and not 

 like the larger vegetables, anchored by stems for life to a particular 

 spot. And with their freedom they possess a power of locomotion 

 which likens them wonderfully to the animals which they so much 

 resemble. Some of them are almost always in rapid motion ; the 

 movements of others are sluggish. But the very same thing is true 

 of the unicellular animals ; for of these, certain forms, as the amnebas^ 

 the actynoj>hrys and the rliizopods execute movements which are 

 almost insensible ; while others are so restless that it is difficult to 

 follow them with the instrument. 



The motions of these minute forms of vegetable life so simulate those 

 of sentient beings, that it is not surprising that they should all have 

 been for a time classed among the animals. But the further dis- 

 covery, due also to the microscope, that the property of locomotion 

 belongs universally to the germ spores and antheridia of all crypto- 

 gamic plants, as is beautifully illustrated in those of all the ferns, 

 mosses, lichens, and fungi, has demonstrated that this property is 

 without any peculiar significancy. The microscope has thus traced 

 the members of the two great kingdoms of the organic world up to 

 a point where all ordinary distinctions fail, and where apparently no 

 real distinction exists. Is there, then, actually no essential or radical 

 difference between the plant and the animal ? And are the wide 

 apparent differences between the higher forms of these organisms, 

 only varying modes of development from germ cells originally essen- 

 tially the same ? This is not by any means the case. Between the 

 unicellular plant and the unicellular animal there is a line of demar- 

 cation as positive as that wliich divides the oak from the elephant. 

 The oak derives its nourishment from the mineral world, the elephant 

 from the organic. Xo animal can live on mineral food, upon earth, 

 or air, or ashes. Ko plant can assimilate organic materials, the flesh 

 of animals or the substance of other plants. Tlie organic matter of 

 soils, or of the fertilizers ap])lied to them, affords no subsistence to 

 the growing crop till by decomposition it ceases to be organic. This 

 distinction is as decided among the minutest and simplest of the 

 forms of living things as among the most conspicuous and complex. 



