90 REMARKS ON CERTAIN [XI. 



might just as well maintain that food is the cause of Infusorian 

 immortality, inasmuch as death ensues when food is withheld. 

 I believe that the essential, fundamental, and original peculiarity 

 of living matter was the power to assimilate and to grow with- 

 out limit. On this depends the existence of the whole organic 

 world : it is a primary power, not a secondary one, and cannot 

 have been conjured up afterwards in the organism by any 

 refined artifice, call it conjugation, fertilization, or anything else. 

 It must have been present from the very beginning of life on the 

 earth. How otherwise could life have persisted up to the first 

 appearance of conjugation or fertilization.'' For there can be 

 scarcely any doubt that neither of these processes is found in 

 the lowest organisms at present known to us. I therefore think 

 that the loss of this fundamental power of unlimited growth 

 must be regarded as a secondary adaptation, called forth by 

 certain special circumstances which rendered it necessary for 

 achieving the combination of different individual hereditary 

 tendencies. When, therefore, certain writers speak of these 

 processes of conjugation and fertilization as a rejuvenescence, in 

 the sense of a renewal of vital energy, I can onl}^ believe that they 

 are upholding a long-vanquished and mystical principle. It is 

 quite otherwise if we speak of the conjugation of Infusoria as a 

 rejuvenescence in the sense of a dissolution and re-formation of 

 many parts : this is a process which may depend throughout 

 on well-known natural forces, and which makes its appearance 

 not only in conjugation but in division also. I have no objec- 

 tion to raise against this kind of rejuvenescence ; in fact the 

 continual repetition of such regeneration among these undying 

 organisms, exposed, as they are, to constant wear and tear, be- 

 comes a necessary assumption. 



In my fourth essay, the idea of fertilization being regarded as 

 a process of rejuvenescence, in the sense of a renewal of vital 

 force, is opposed, and the converse view is clearly enunciated. 

 To condense my argument into a sentence, — we ought not to 

 speak, as formerly, of the two conjugating nuclei of the germ- 

 cells as male and female, but as paternal and maternal; they are 

 not opposed to each other, but are essentially alike, differing 

 only as one individual differs from another of the same species. 

 Fertilization is no process of rejuvenescence, it is nothing more 

 than a mingling of the hereditary tendencies of two individuals. 



