234 THE NATURE AND ORIGIN OF LIFE 



evolution that takes place in a lineage of individuals with 

 the individual evolution of an eternal individual which, 

 from time to time, should undergo a moulting yet more 

 complete than that of these crustaceous animals and should 

 periodically become a plastic mass capable of fabricating 

 for itself an entirely new equilibrium. 



Thus the evolution of a line of individuals inevitably 

 receives, if not a definitely discontinuous character, at 

 least the aspect of an ascent of steps, of which each indivi- 

 dual represents one, according to the happy expression of 

 Professor Giard. 



Even when the transformations which touch the heredi- 

 tary patrimony are entirely continuous, the difference be- 

 tween two individual adults following each other in the 

 lineage must be " finite." Consequently, the question 

 whether variation has been slow or sudden in the series of 

 ancestral forms of present species loses its seeming character 

 of precision. That which mathematically would have had 

 an exact meaning if specific evolution had been continuous 

 or discontinuous, is no longer in question, but only whether 

 the discontinuities which fatally exist between two suc- 

 cessive individuals finite discontinuities, as we have seen 

 are small or great. As the words small or great have no 

 absolute meaning the interest of the question is lost. 



In the individual evolution of certain living beings the 

 last moult is accompanied by so wonderful a transform- 

 ation that the individual issues from it quite unrecogniz- 

 able. From a caterpillar it becomes a butterfly surely 

 a noteworthy variation. For this the name of metamor- 

 phosis has been reserved. Such a phenomenon is easily 

 explained when we think how the genital organ, a morpho- 

 genic parasite, evolves at the same time as the host within 

 which it is lodged and that a transformation in the state 



