176 THE POPULAR SCIENCE MONTHLY. 



armed with the most effective aids supplied by modern science, has 

 only recently remarked, after a long time, that any change has taken 

 place. 



In reality every living body is subject to an uninterrupted change, 

 which goes on in an appointed course. Life is like a stream, which 

 gushes out of a hidden spring ; slowly increases, flows on for a time 

 with even strength, finally with diminishing velocity, to disappear in 

 the sea of eternity. We designate the course of changes which every 

 living being, plant, and animal, as well as man, goes through, as its 

 development. Development begins with the moment of birth and 

 ends with death. 



But with the death of the single being its race does not disappear ; 

 the property dwells in every living being by which a part of it can 

 drop off from the whole, continue to develop itself independently, 

 be nourished and rejuvenated by a change of matter. We call this 

 dropping off of a part, capable of development, from the whole, propa- 

 gation ; with propagation is transferred the history of development ; 

 the separated part, which we denote as an egg or spore, a seed or 

 embryo, a bud or spawn-knob, passes in substance through the same 

 course of changes as the whole from which it has been separated. 

 Like arises from like ; the children resemble their parents, and, as these 

 again resemble their ancestors, the character of the species is kept up 

 essentially unchanged, in spite of the perishability of individuals, 

 through all the generations. 



That life is nothing but a constant development and an uninter- 

 rupted rejuvenation is expressed in the plainest and clearest manner 

 in the world of plants. It is, indeed, not easy to comprehend the life 

 of plants aright, and many regard the term as a figure of speech, not 

 properly applied. Plants, they say, do not feel or move ; they have 

 no consciousness, no soul, like animals ; how can we speak of their life ? 

 If motion, feeling, and consciousness alone constituted life, there might 

 be some doubt as to whether plants lived, though it would still be 

 worth while to inquire whether these higher attributes were really 

 wanting in plants. Darwin has lately shown, in connection with many 

 older observations, that all the parts of plants participate in a regular 

 circling motion, and that single organs show sensibility enough to 

 make them comparable with the brains of the lower animals. But 

 when, instead of the highest acts of life, we confine ourselves to its 

 general and essential manifestations, it becomes undoubtedly clear 

 that plants are living in the same sense as animals and men. Only 

 plants are distinguished, not from animals generally, but from the 

 higher animals that rank nearest to men, and from which our concep- 

 tions of animal life in general have been formed, in that in them unity, 

 or individuality, is expressed in a much more imperfect manner. The 

 mammal, bird, fish, insect, is a separate, single, and indivisible being. 

 Its members are fixed and limited in number ; not one of them can 



