Thus a new cell is produced. This process is similar to the
conjugation of two unicellular beings, such as two acinetiform
infusoria, one of which, the female ([Symbol: Female]), is larger than
the other, the male ([Symbol: Male]). This difference of size in the
conjugating cell is, however, without importance.
From this double cell produced by conjugation many generations of
cells arise by continual cell division in divergent series. Among the
infusoria these are all immortal, but many of them are destroyed, and
only a few persist till conjugation again takes place. The same is the
case with man. Numerous series of cell families arise, which are all
immortal: of these but few--strictly speaking, only one--live till the
next period of conjugation and then give the impulse which results in
the formation of a new diverging series of cells. The difference
between man and the infusorian is only that in the former the cells
which originate from the double cell (the fertilized ovum) remain
together and become differentiated one from another, while in the
latter the cells are usually scattered but remain alike in appearance,
etc.
The seeds of death do not lie, as Weismann appears to assume, in the
differentiation of the cells of the higher animals.
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