522 THE POPULAR SCIENCE MONTHLY. 



really only the grouping made in our mind of all the living indi- 

 viduals exhibiting the same form, and which we believe to be all 

 united under a common parentage. 



Yet form can not serve of itself to characterize life, for there 

 exist other bodies than crystals in the inorganic world which are 

 individuals. The planets and the rings of Saturn will at once 

 occur as examples. We might also range in the same category 

 comets and whirls of smoke, which are likewise individuals, and 

 cease to be by the mere fact of their division or dissociation. 



Form is therefore not sufficient to characterize the living indi- 

 vidual. Let us see if the general features and external aspect of 

 organized beings will not offer us marks to distinguish them from 

 mineral bodies. The plane faces, the sharp edges, and the definite 

 angles of crystals, and the spherical contours of the heavenly 

 bodies, have been contrasted with the undulating surfaces, the 

 less geometrical and more softly defined profiles of plants and 

 animals. This trait is certainly not destitute of value, and the 

 untrained mind is rarely deceived by it. Sometimes the lapidary, 

 in cutting agate, uncovers delicate arborescent shapes in the trans- 

 parency of the gem. The illusion is vivid, and one might fancy 

 he had a petrified moss under his eyes. A lens will assure him 

 that there is no vegetable fossil here, and will reveal an assem- 

 blage of crystalline needles that have nothing in common with 

 the delicate articulations and waving lines of a genuine moss. 



Its particular stamp is so clearly impressed on each living be- 

 ing and on each of its parts, and it is s6 recognizable that it guides 

 the naturalist with certainty, even when he affirms, from the 

 smallest remnant or weakest impression, the existence on the sur- 

 face of the globe, in prodigiously distant times, of beings that 

 lived then, and with which he is unacquainted. Some of the or- 

 ganisms have left only traces, and he affirms that life passed there, 

 without knowing whether it was vegetable or animal. 



The ancients, although they had not our experience in inter- 

 preting the true nature of fossils, never failed to recognize the 

 factory mark which Nature impresses on its works. Science then 

 gave no means of discerning in ammonites the shell of an animal 

 allied to the squids and cuttlefish ; but the finders had at least 

 the feeling that these things had lived, and, by analogy, they saw 

 in them the bones of animals preserved in the earth. 



Form is not an essential attribute of life. There exist living 

 beings destitute of living form, as there exist chemical substances 

 that do not crystallize. The microscope reveals in stagnant water 

 gelatinous masses that change their form and move incessantly. 

 We see a part of the mass stretch out like a foot advancing. Then 

 the whole being seems to pass into this prolongation, which is 

 proportionately swelled out. Another expansion occurs at an- 



