In these processes it often
happens that the whole body of the mother, the entire cell, may
resolve itself into two or more children; at times, however, a small
portion of the mother cell remains unused. This remnant, in the
spore-forming unicellular plants represented by the cell wall, is then
naturally dead.
From this it follows that these unicellular beings are immortal. The
mother cell divides, the daughter cells resulting from the first
division repeat the process, the third generation does the same, and
so on. At each division the mother cell renews its youth and
multiplies, without ever dying.
External circumstances can, of course, at any moment bring about the
death of these unicellular organisms, and in reality almost every
series of beings which originate from one another in this way is
interrupted by death. Some, however, persist. From the first
appearance of living organisms on our planet till to-day, several such
series--at the very least certainly one--have persisted.
The immortality of unicellular beings is not at any time absolute, but
only potential. Weismann has recently directed attention to this
point. External occurrences may at any moment cause the death of an
individual, and in this way interrupt the immortal series; but in the
intimate organization of the living plasma there exist no seeds of
death.
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