^22 Kkport S.A.A. Advancemeni of Science. 



2. THE POSSIBILITY OF STIMIT.I P.KING STORED LP IN' 

 IHE OROAMSM SO AS !'( » PRODL'CE AFTER- 

 EFFECTS. AND IHE INHERITANCE OF AC(^CIRED 

 CHARACTERS. 



We may then lake it a.s an eslal dished fact that the environment 

 influences the inflividual organism in such a manner as to call forth 

 modifications which in some cases at anv rate are of an adaptive 

 character, but it has Ijeen vehementlv denied, by Weismann and his 

 followers, that such modification, pnxUiced during the lifetime of 

 the individual, (^an be handed on from one generatiijn to the next ; 

 in other words, that "acquired characters" can be transmitted from 

 jian-nt to offspring. 



In one of his earliest essays" on this subject, Weismann ob- 

 serves : — " The difficulty or the impossibilit) of rendering the trans- 

 mission of acquired characters intelligible l)y an appeal to any known 

 force has been often felt, but no one has hitherto attempted to cast 

 doubts upon the very e.xistence of such a form of heredity." . 

 He then proceeds to evade the difficult} in question bv denying the 

 existence of the phenomenon to be explained : " It has never been 

 proved,'' he .says, " that acquired characters are transmitted, and it 

 has never been demonstrated that, without the aid of such trans- 

 mission, the evolution of the organic world becomes unintelligible.' f 

 He also quotesj from Du Rois Reymond the statement that " the 

 hereditary transmission of acquired characters remains an unin- 

 telligible hypothesis, which is only deduced from the facts which it 

 attempts to exj)lain." 



Weismann's own theor\ of the continuity of the germ-plasm 

 is. as is well known, an elaborate attempt to account for the 

 phenomena of organic evolution without calling in the aid of the 

 transmission of acquired characters, and he devotes an immen.se 

 amount of ingenious argument to this object. " The understanding 

 of the ])henomena <jf heredity,'' he ol)serves, " is cjnly possible on the 

 fundamental supposition of the continuitv of the germ-plasm. "§ 



It is impossible in the space at our disposal to follow Weismann 

 in the laborious arguments b\ which he attempts to discredit the 

 cases of transmission of acquired characters which have been brought 

 forward in evidence against his own views, but it is of first importance 

 in an\ discussion of ihe subject to be perfecilv clear what Weismann 

 himself means 1)\ an acquired character. " New characters. " he 

 points out. " ma\ arise in \arious wa\s. In artificial or natural selec- 

 tion, by the spontaneous variations of the germ, or by the direct 

 effects of external influences upon the body, including the use and 

 disu.se of parts. If we assume diat these latter characters are tran.s- 

 mitted, the further 'assumption of comj)licated relations between the 



* Essays upon Hcrfditv. Engli^li Translation. iS,S(). p. So. 

 -\ Ct iit, p. 8 1 . 1 Ct cit, p. 82. i? Lo, fit. 1 04. 



