l6S THE EVOLUTION OF MAN. 



though certain stages seem omitted, the continuity is really 

 unbroken, and that each new form arises directly from that 

 which preceded it. Throughout there is a causal and un- 

 broken connection ; noAv^here a sudden leap.^"^ But when the 

 rapidity of the process of evolution is at one time retarded 

 and again suddenly accelerated, or when heredity is cur- 

 tailed, the result of the process appears to be a sudden leap. 



This unbroken causal connection of the processes of 

 evolution exists equally in germ-history, and in tribal 

 history. For as Ontogeny is but a brief reproduction of 

 Phylogeny, conditional on Heredity and modified by 

 Adaptation, in the latter, therefore, as in the former, no leap 

 or open gap can ever really exist between two consecutive 

 evolutionary forms. As in the evolution of the individual 

 so in that of the species, each new form arises directly from 

 that which preceded it ; and here also the physiological 

 process of development always preserves its continuity. 

 Even in those extreme cases where a new form does indeed 

 seem to come into existence quite suddenly, as in what is 

 called " sudden or monstrous adaptation," there is always, 

 under the surface, an unbroken physiological evolutionary 

 process which has the appearance of being a " sudden leap " 

 only because of its comparative rapidity, or of the magnitude 

 of its result. 



As a striking instance, let us consider a frequently ob- 

 served case of such "sudden variation." A common two- 

 horned he-goat, the consort of which is also a common two- 

 horned goat, begets a kid, from the skull of which grow four 

 horns, in place of the two horns previously hereditary in this 

 family of goats. In this case a new variety of goats bear- 

 ino- four horns has " suddenly " arisen, and under favourable 



