Weismannism tip to date (1893). 167 



the function of causing variability 1 ; while Galton's 

 hypothesis, which supposes the object of this form of 

 propagation to be that of conserving the "germs" 

 ( = " determinants") of the phyla, has a good deal 

 to say for itself 2 . Of course such alternative hypo- 



1 " Rejuvenescence " means the renewal of vital energies which is 

 supposed to result from a fusion of the contents of two cells. For an 

 excellent discussion of this and the other theories on the object of sexual 

 propagation, see a brief article by Professor Marcus Hartog, in the 

 Contemporary Review for July, i S92 . Since then Weismann has published 

 The Germ-plasm, and here his main argument against this theory is that 

 tens, or even hundreds of generations of unicellular organisms have been 

 observed to succeed one another before any act of conjugation takes 

 place. But I cannot see that it signifies how many generations may in 

 different species be proved capable of resulting from a single act of con- 

 jugation. Weismann himself now accepts the analogy between cell- 

 proliferation as resulting from conjugation in unicellular organisms, and 

 from fertilization in multicellular. But even three hundred generations 

 of the former can scarcely be regarded as equal to all the " ontogenetic 

 stages" of the latter. 



2 This view of the function of sexual propagation is now universally 

 ascribed to Strasburger, and it is quite true that he has independently 

 adduced it. But as this was not done until about ten years after it had been 

 published by Galton, I have designedly associated the idea with Galton's 

 name. The following are the words in which it was announced 

 by him : — 



" The necessity of a system of double parentage in complex organisa- 

 tions is the immediate consequence of a theory of organic units and 

 germs, as we shall see if we fix our attention upon any one definite series 

 of unisexual descents, and follow out its history. Suppose we select, 

 cut off, and plant the second bud, then after it has grown to maturity we 

 similarly take the second of its buds, and so on consecutively. At each 

 successive stage there is alwa} s a chance of some one or more of the 

 various species of germs in the stirp dying out, or being omitted ; and of 

 course when they are gone they are lost for ever, and are irreplaceable 

 by others. From time to time this chance must fall unfavourably, and 

 will cause a deficiency in some of the structural elements, and a conse 

 quent deterioration of the race. If the loss be vital, this particular line 

 of descent will of course be extinguished at once ; but on the more 

 favourable supposition, the race will linger on, submitting to successive 

 decrements in its constituent elements, until the accumulation of small 

 losses becomes fatal." — loc. cit., p. 333. 



Galton also points out a further advantage that is secured by 



