180 Darwin and Embryology 



Lamarck's "acquired characters"? They are variations in genetic 

 characters caused in a particular way. There are, in fact, two kinds 

 of variation in genetic characters depending on the mode of causa- 

 tion. Firstly, there are those variations consequent upon a variation 

 in the constitution of the protoplasm of a particular zygote, and 

 independent of the environment in which the organism develops, 

 save in so far as this simply calls them forth : these are the 

 so-called genetic or mutational variations. Secondly, there are 

 those variations which occur in zygotes of similar germinal con- 

 stitution and which are caused solely by differences in the environ- 

 ment to which the individuals are respectively exposed : these are 

 the "acquired characters" of Lamarck and of authors generally. 

 In consequence of this double sense in which the term "acquired 

 characters" may be used, great confusion may and does occur. If 

 the protoplasm be compared to a machine, and the external con- 

 ditions to the hand that works the machine, then it may be said that, 

 as the machine can only work in one way, it can only produce one 

 kind of result (genetic character), but the particular form or quality 

 (Lamarckian "acquired character") of the result will depend upon 

 the hand that works the machine (environment), just as the quality 

 of the sound produced by a fiddle depends entirely upon the hand 

 which plays upon it. It would be improper to apply the term 

 " mutation " to those genetic characters which are not new characters 

 or new variants of old characters, but such genetic characters are of 

 the same nature as those characters to which the term mutation has 

 been applied. It may be noticed in passing that it is very questionable 

 if the modern biologist has acted in the real interests of science in ap- 

 plying the term mutation in the sense in which he has applied it. The 

 genetic characters of organisms come from one of two sources : either 

 they are old characters and are due to the action of Avhat we call in- 

 heritance or they are new and are due to what we call variation. If 

 the term mutation is applied to the actual alteration of the machinery 

 of the protoplasm, no objection can be felt to its use; but if it be 

 applied, as it is, to the product of the action of the altered machine, 

 viz. to the new genetic character, it leads to confusion. Inheritance 

 is the persistence of the structure of the machine; characters are 

 the products of the working of the machine; variation in genetic 

 characters is due to the alteration (mutation) in the arrangement 

 of the machinery, while variation in acquired characters (Lamarckian) 

 is due to differences in the mode of working the machinery. The 

 machinery when it starts (in the new zygote) has the power of 

 grinding out certain results, which we call the characters of the 

 organism. These appear at successive intervals of time, and the 

 orderly manifestation of them is what we call the life-history of the 



