90 The Science of Life. 



pushing ideas to their logical limits, who startled biolo- 

 gists by the conception of the immortality of the sim- 

 plest organisms the unicellular Protozoa and Proto- 

 phytes. 



It is "not difficult to see that these cannot be subject to 

 death in the same degree as higher animals are. 



(1) In the first place, being single cells, without any 

 "body", they are able to sustain the equation between 

 waste and repair for an indefinitely long period. It is 

 conceivable that some of the simplest may have been 

 living on since life began. They make good their 

 waste by continuous and perfect repair. This has been 

 summed up in the epigram that death was the price 

 paid for a body. 



(2) In the second place, it is a well-known fact that 

 among multicellular organisms reproduction is attended 

 with loss of life. One of the simplest an Orthonectid 

 dies in giving birth, and the same is true of some 

 worms. Death follows close on the heels of reproduc- 

 tion in the case of animals so different as may-flies, 

 butterflies, and lampreys. Everyone knows that flower- 

 ing and fruiting exhaust the energies of annual plants. 

 In the very morning of life immortality was pawned for 

 love. 



In the Protozoa and Protophytes, however, where the 

 distinction between "body" and reproductive elements 

 has not been differentiated, reproduction is a simpler, less 

 expensive process. The Amoeba divides into two, only 

 a metaphysical individuality is lost. There is as little 

 death as when two cells fuse into one, another familiar 

 reproductive phenomenon. Similarly, with spore-forma- 

 tion and budding, we cannot speak of death when there 

 is nothing not even ashes left to bury. More pro- 

 saically it may be said that the conception of natural 

 death which applies to the multicellular organisms does 

 not apply in the same degree to those which are uni- 

 cellular. 



Maupas has indeed pointed out that an isolated family 

 of Infusorians, all descended by asexual multiplication 

 from one cell, and therefore not coupling or conjugating 

 with one another, will, after a certain number of genera- 



