216 LECTURES ON BIOLOGY 



man whose arm or legs have been amputated is no longer 

 himself: that the healthy man is dead, and that the cripple is 

 a new individual which did not exist before. No one would 

 seriously maintain such an absurdity, and the patient himself 

 would most energetically protest against such suggestions. 



How large the part of the body is which I cut away from the 

 Amoeba or any other organism cannot in any way affect this con- 

 sideration. It does not matter whether I take away a minute 

 particle or half of the Amoeba cell-body, so long as the animal- 

 cule is able to survive the operation. Equally so it is without 

 importance which part of the body is lost, whether it consists 

 only of protoplasm or of nuclear substance, or whether it was 

 an eye, or an arm, or leg that was destroyed. 



Let us now assume that I divide an Amosba in such a manner 

 that both halves are equally large and that both contain proto- 

 plasm as well as a share of the nucleus. Let us call these two 

 pieces A and B, and trace their future fate. A closes its wound 

 in a short time, rolls itself up, and begins to act like a healthy 

 animalcule. It crawls about, eats, and grows. Before long the 

 damage has been repaired and everything is exactly as it was 

 before. As regards A, therefore, we stand towards it in the same 

 position as we stood towards the wounded Amoeba, i.e., A is no 

 newly-generated creature, but the old Amoeba cut in two, which 

 has not died but continues to live in spite of the terrible mutila- 

 tion, and continues its individuality uninterrupted in A. We 

 cannot, therefore, speak here of death and dying. 



But what has in the meantime ^become of the other piece ? 

 Has it perished like the smaller particles of protoplasm which we 

 cut off before ? Here, too, we find that it has developed precisely 

 like A, and become a complete Amoeba. But because B also 

 remained alive can we conclude post festum that A is dead, in 

 spite of all observation to the contrary ? No, the only conclusion 

 which we are justified in drawing is that the original Amoeba is 

 not only not dead but has doubled its individuality and continues 

 to exist undiminished in A and B. 



What I have done here by an artificial operation does not 

 differ fundamentally from the natural manner of reproduction by 

 fission. We must therefore acknowledge that the natural act of 

 reproduction is not bound up with a process of dying, but only 



