666 The American Naturalist. . [August, 
of the other, neither is older, neither is parent, but each 
has partaken of the common stock of protoplasm. The pro- 
toplasm again multiplies itself in the two organisms, and at 
length it is again divided; and so, to the end of time, the re- 
motest individual of the series may be said to contain a por- 
tion of the original protoplasm ; in other words, the protoplasm 
is continuous. And inasmuch as protoplasm is the seat or 
physical basis of life, it may be said that the one-celled 
organism is immortal, or is not confronted by natural 
death. 
In time, however, there came a division of labor—cells liv- 
ing together in colonies, and certain cells performing one 
function and certain other cells other functions. This was, 
perhaps, the beginning of the many-celled organism, in which 
certain cells developed the specific function of reproduction, 
or eventually became elements of sex. As organisms became 
more complex in their structure, there came to be great differ- 
ences between this reproductive or germ portion and the sür- 
rounding or body portion; and Weismann assumes that these 
two elements are different and distinct from each other in 
kind, and that inasmuch as the one-celled organisms propa- 
gated their exact kind by simple division, that therefore the 
reproduetive elements of the many-celled or complex body 
must continue to perpetuate their kind or enjoy immortality, 
while all the surrounding or body cells die and are reproduced 
only through the reconstructive power of the sexual elements. 
There are, then, according to this hypothesis, two elements or 
plasms in every organized being, the germ-plasm and the 
soma-plasm or body-plasm ; and every organism which pro- 
creates thereby preserves its germ-plasm to future generations, 
while death destroys the remainder. A vital point in this 
hypothesis is the method by which the soma-plasm, or the 
organs and body of the organism, can be so impressed upon 
the germ that they shall become hereditary. At first it would 
seem as if some assumption like that of Darwin's might be 
useful here—that this germ-plasm is impressed by particles 
thrown off from all the surrounding or soma-cells; but this 
Weismann considers to be too unwieldy, and he ascribes the 
