LIFE AND DEATH. 143 



cells. But I find no difficulty in believing- that variations in these 

 cells took place during- the transition from Homoplastids to Hetero- 

 plastids, variations which formed the material upon which the un- 

 ceasing- process of natural selection could operate, and thus led to 

 the differentiation of the previously identical cells of the colony 

 into dissimilar ones some becoming- perishable somatic cells, and 

 others the immortal reproductive cells. 



It is at any rate a delusion to believe that we have explained 

 natural death, by deriving it from the starvation of the soma of the 

 Orthonectides, by the aid of the unproved assumption of the trans- 

 mission of acquired variations. We must first explain why these 

 organisms produce only a limited number of reproductive cells 

 which are all extruded at once, so that the soma is rendered help- 

 less. Why should not the reproductive cells ripen in succession as 

 they do indirectly among- the Monoplastides, that is to say in a 

 succession of g-enerations, and as they do directly in great num- 

 bers among the Metazoa ? There would then be no necessity for 

 the soma to die, for a few reproductive cells would always be pre- 

 sent, and render the persistence of the individual possible. In 

 fact, the whole arrangement the formation of reproductive cells 

 at one time only, and their sudden extrusion, presupposes the 

 mortality of the somatic cells, and is an adaptation to it, just as 

 this mortality itself must be regarded as an adaptation to the 

 simultaneous ripening and sudden extrusion of the generative cells. 

 In short, there is no alternative to the supposition stated above, 

 viz. that the mortality of the somatic cells arose with the differ- 

 entiation of the originally homogeneous cells of the Polyplastids 

 into the dissimilar cells of the Heteroplastids. And this is the 

 first beginning of natural death. 



Probably at first the somatic cells were not more numerous than 

 the reproductive cells, and while this was the case the phenomenon 

 of death was inconspicuous, for that which died was very small. 

 But as the somatic cells relatively increased, the body became of 

 more importance as compared with the reproductive cells, until 

 death seems to affect the whole individual, as in the higher 

 animals, from which our ideas upon the subject are derived. In 

 reality, however, only one part succumbs to natural death, but it is 

 a part which in size far surpasses that which remains and is im- 

 mortal, the reproductive cells. 



