IMMORTALITY OF PROTOZOA 233 



cess of conjugation has yet been observed in Amoeba and 

 Euglena; and that, in Actinospheerium, the gametes are the 

 identical pairs of so-called secondary cysts formed by the 

 binary division of the primary cysts, modified only to the extent 

 of their having ejected part of their nuclear matter in the form 

 of polar bodies. Amongst so many seeming contradictions it 

 is as yet impossible to lay the foundations of a solid theory. 



Much has been said of late years of the potential immortality 

 of Protozoa. But the facts described for Copromonas, Poly- 

 toma and Paramecium, as well as those about to be described 

 for Vorticella, show that these creatures, like the higher forms 

 of life, are subject to the inexorable laws of decay and death. 

 If it should be established beyond doubt that Amoeba (or any- 

 other Protozoon) is capable of multiplying itself indefinitely by 

 binary division, without loss of functional activity calling for 

 repair by means of conjugation, then indeed it could be said 

 that these organisms are immortal in that decay and death 

 would not come to them of necessity, but as an accident, 

 through deprivation of food or violence. But we know too 

 little of the life history of Amoeba to allow of our making any 

 positive assertion about it, and the same may be said of most 

 other Protozoa. We must be content at present with the posi- 

 tive evidence afforded by the life-histories of Paramecium and 

 allied forms, which demonstrate that the organism would wear 

 out and perish were it not refreshed, rejuvenated from time to 

 time, by the act of conjugation. How it is that conjugation 

 rejuvenates the enfeebled organisation we cannot say. 



But it must be remernbered, whilst we admit decay and 

 death as the natural accompaniments of existence, that the life- 

 stuff, protoplasm in its widest sense, is immortal. All the 

 evidence at our disposal forces us to believe that living matter 

 can only be born from living matter. Organisms are not bred, 

 as was once believed, from slime and mud, but only from other 

 organisms, and all that now lives on the earth is descended 

 from that original life-stuff whose origin will ever be a mystery 

 to us. 



