BETWEEN ANIMALS AND PLANTS. 151 



But now, to go back to the lowest of them, the spore-like 

 forms, let me recall, in a word, what are the animal-like character- 

 istics of their organization. They are, contractility of the body, 

 the pulsation of an organ called the contractile vesicle, and the 

 Introception of food, none of which have been recognized in 

 the spores of any of the aquatic plants which most resemble 

 these infusorians in external conformation. 



Now this would appear to settle the confusion which had 

 mingled such a mass of heterogeneous material; and the zoolo- 

 gist, on the one hand, would be enabled to draw his inferences 

 without fear of imposing upon animals those characteristics 

 which, on the other hand, the botanist might claim for the special 

 objects of his study. But it would seem to be a vain hope, and 

 the work of the physiologist and the microscopist has but just 

 begun ; for to this day there remains a doubt as to the animal 

 or vegetable nature of certain forms, which have characters that 

 lead on the one side to plants, and on the other to animals. 



The investigation of this apparently twofold relation is per- 

 haps by far the most important among all the researches of the 

 present day upon the subject of spontaneous generation and the 

 development theory ; for if this twofold relation is not apparent, 

 but real, then there is no distinction between animals and plants. 



What test, therefore, can we apply to those doubtful forms 

 which I have spoken of, in order to prove that they are either 

 living, sentient beings, or that they are as devoid of sensation 

 as the grass of the field. It would seem almost absurd to un- 

 dertake such a thing as the proving of a self-evident difference 

 between a weed and the animal which feeds upon it; but when 

 we reflect upon how many characters the two have in common, 

 such as life, growth, circulation of fluids through the tissues, a 

 remarkably similar, in fact, almost identical cellular structure in 

 many cases, and finally a closely related mode of reproduction ; 

 I say in reflecting upon these more or less common characteris- 

 tics, the apparent absurdity rises to a dignity worthy of the mind 

 of the most gifted genius ; and when naturalists are accused, 

 by the unthinking, of trifling over these little things, these minute 



