INHERITANCE 115 



transmitting hereditary characters to the germ- 

 plasma ; and asserts that the power is due to the 

 special and utterly unknown molecular constitution 

 of this germ-plasma, the very existence of which is 

 altogether hypothetical. 



A more valuable part of Weismann's work con- 

 cerns the share which sexual reproduction takes, in 

 his opinion/as the direct cause of specific variation. 

 Inasmuch as the germ-plasma is supposed to be 

 of constant composition, and to be transmitted 

 unchanged from generation to generation, it follows 

 that characters acquired by the parent cannot be 

 transmitted to the offspring. This statement, that 

 acquired characters are not inherited, is one that 

 has attracted much attention, and that at the 

 present time is being most keenly debated. 

 Should it prove to be true, it becomes necessary to 

 look elsewhere for the cause of specific variation in 

 animals : and this, Weismann maintains, is to be 

 found in the mingling of germ-plasma from two 

 separate animals in the act of fertilisation of the 

 ovum by a spermatozoon. 



Limits, both of time and space, forbid that I 

 should follow these arguments further. We are at 

 present very ignorant concerning the nature, 

 properties, and reactions of living things, while life 

 itself remains as great a mystery as ever. Perhaps 

 it will not be until we have gained some clue to the 

 mystery that we shall be able to understand what 

 is the real nature of inheritance : in the meantime 

 we may heartily welcome all earnest efforts towards 

 the solution of the problem. 



