LIFE AND DEATH. 141 



might have been achieved, just as it was possible at a later period, 

 in the higher Metazoa, to prolong- both the duration of life and of 

 reproduction a hundred- or a thousand-fold. At any rate, no reason 

 can be given which would demonstrate the impossibility of such an 

 achievement. 



With our inadequate knowledge it is difficult to surmise the 

 immediate causes of such a selective process. Who can point out 

 with any feeling of confidence, the direct advantages in which 

 somatic cells, capable of limited duration, excelled those capable 

 of eternal duration? Perhaps it was in a better performance of 

 their special physiological tasks, perhaps in additional material 

 and energy available for the reproductive cells as a result of this 

 renunciation of the somatic cells ; or perhaps such additional 

 power conferred upon the whole organism a greater power of 

 resistance in the struggle for existence, than it would have had, 

 if it had been necessary to regulate all the cells to a corresponding 

 duration. 



But we are not at present able to obtain a clear conception of 

 the internal conditions of the organism, especially when we are 

 dealing with the lowest Metazoa, which seem to be very rarely 

 found at the present day, and of which the vital phenomena we 

 only know as they are exhibited by two species, both of doubtful 

 origin. Both species have furthermore lost much of their original 

 nature, both in structure and function, as a result of their parasitic 

 mode of life. Of the Orthonectides and Dicyemidae we know 

 something, but of the reproduction in the single free non-parasitic 

 form, discovered by R E. Schulze and named by him Trichoplaos 

 adhaerens, we know nothing whatever, and of its vital phenomena 

 too little to be of any value for the purpose of this essay. 



At this point it is advisable to return once more to the derivation 

 of death in the Metazoa from the Orthonectides, as Gotte en- 

 deavoured to derive it, when he overlooked the fact that, according 

 to his theory, natural death is inherited from the Monoplastids and 

 cannot therefore have arisen anew in the Polyplastids. According 

 to this theory, death must necessarily have appeared in the lowest 

 Metazoa as a result of the extrusion of the germ-cells, and by con- 

 tinual repetition must have become hereditary. We must not how- 

 ever forget that, in this case, the cause of death is exclusively 

 external, by which I mean that the somatic cells which remained 



