28 BRITISH FliKSH WATER RH1ZOPODA. 



reproductive cell being itself and alone the individual 

 Protozoan, there is nothing to die, nothing to be cast off 

 by the reproductive cell when entering on a new career 

 of fission. . . . Experiment and observation in this 

 matter are extremely difficult, but we have no reason 

 to suppose that there is any inherent limit to the pro- 

 cess of nutrition, growth, and fission, by which con- 

 tinuously the Protozoa are propagated. The act of 

 conjugation from time to time confers upon the proto- 

 plasm of a given line of descent new properties, and 

 apparently new vigour. Where it is not followed by a 

 breaking-up of the conjugated cells into space, but by 

 separation and renewed binary fission (Ciliata), the 

 result is described simply as ' rejuvenescence.' ' 



This theory, which Ehrenberg first suggested, seems 

 to us to be based upon insufficient data. The available 

 evidence is directly opposed to such a supposition as 

 the immortality of living matter in any form. The 

 protoplasmic cell does " die and disintegrate." Oppor- 

 tunities for observation, it is true, are rare. One, 

 within our own experience, may be worth placing on 

 record here. During an examination of pond-water 

 an Amoeba entered the field of view, in the condition 

 represented in figure 15<7. The main body was 

 advancing in Amoeba fashion by lobular expansions 

 anteriorly, but dragging behind a trail of its own 

 protoplasmic substance. This was clearly an abnormal 

 condition, and in endeavouring to account for it one 

 was led to suppose that the organism had somehow 

 met with an accident by which its body had been so 

 torn as to form a kind of tail with a terminal bulb, 

 about midway between which and the main body there 

 was a slight thickening. 



Curiosity led us to keep the animal under observa- 

 tion for about an hour and a half. During that period 

 the terminal bulb became separated and assumed a 

 spherical shape (c) ; afterwards the middle portion 

 separated ; and at last the main body ceased to show 

 any indication of life, and rounded out into a spherical 



