THE INHERIT ANCE OF ACQUIREMENTS 83 



of gross injury l)y exlerniil iigencies. In short, I he 

 a posterioH evidence tends, on the whole, to negative 

 the theory that acquirements are transmitted, but 

 cannot be regarded as conclusive. 



If, however, we consider certain facts of very lowly 

 organisms, we do seem to find positive evidence. 

 Haeckel, for instance, tirmly behoves in the inherit- 

 ance of acquirements, and cites certain known tacts 

 of bacterial life. Disease-producing bacteria p;ussed 

 through the body of a susceptible animal are found 

 to be increased in virulence. It is their favourable 

 environment that confers upon several generations of 

 bacteria their acquired exaltation of virulence, and 

 they certainly transmit it to their descendants. 

 Here, indeed, appears to be a conclusive instance of 

 the transmission of an acquirement. 



Thus we are compelled to leave this controversy 

 unsettled. We may tentatively incline, however, to 

 the following conclusions : — 



The transmission of certain accjuirements is not 

 incompatible with Weismann's theory of heredity, 

 and is perfectly compatible with Her twig's theory, 

 which is far from being disproved. 



Certain instances of transmission of acquirements 

 appear to be known. 



The transmission of acquirements is far more 

 limited, assuming it to occur at all, than used to bo 

 thou'dit. 



However fully it were admitted, it could not ex- 

 plain all the facts of organic evolution. 



Numberless supposed instances of the transmission 

 of acquirements can be more easily and satisfactorily 

 explained by means of the theory of natural selection. 



