III.] LIFE AND DEATH. I35 



mentioned cases we have to do with adaptation to certain very 

 special conditions of existence— an adaptation leading to an 

 immense development of reproductive cells in a mother or- 

 ganism which can no longer take in nourishment, or which has 

 become entirely superfluous because its duty to its species is 

 already fulfilled. If this is an example of death inherent in the 

 essential nature of reproduction, then so is the death of a mature 

 segmentof a tape-worm in the gastric juices of the pig that eats it. 



With Gotte, the conception of reproduction, like the concep- 

 tion of death, is a protean form, which he welcomes in any 

 shape, if only he can use it as evidence. If death is a necessary 

 consequence of reproduction, its cause must be always essen- 

 tially the same, and might be expressed in one of the following 

 suggestions: — (i) in the necessity for a / re-coining' of the 

 protoplasm of the germ-cells ; but here death could only affect 

 the germ-cells themselves : (2) perhaps in the withdrawal of 

 nourishment by the mass of developing reproductive material, 

 just as death occurs sometimes among men by the excessive 

 drain on the system caused by morbid tumours : (3) or in 

 consequence of the development of the offspring in the body of 

 the mother ; this however would only affect the females, and 

 could therefore have no deep and general significance : (4) 

 from the extrusion of the sexual cells, — ova or spermatozoa, — 

 and in the impossibility of further nourishment which is con- 

 sequent upon this extrusion — (Orthonectides .') : or (5) finally 

 in an excessively powerful nervous shock brought about by the 

 ejection of the reproductive cells. 



But no one of these alternatives is the universal and inevitable 

 cause of death. This proves irrefutably that death does not 

 proceed as an intrinsic necessity from reproduction, although it 

 may be connected with the latter, sometimes in one way and 

 sometimes in another. But we must not overlook the fact that 

 in many cases death is not connected with reproduction at all ; 

 for many Metazoa survive for a longer or shorter period after 

 the reproductive processes have ceased. 



In fact, I believe I have definitely shown that no process 

 exists among unicellular animals which is at all comparable 

 with the natural death of the higher organisms. Natural death 

 first appeared among multicellular beings, and among these first 

 in the Heteroplastids. P^urthermore, it was not introduced 



