Modification of Germinal Constitution of Organisms 257 



provisional h\pothesis of pangenesis, the id-determinant- 

 biophore fabric of Weismann, or the pangene complex of 

 DeVries. Much has been written concerning the uselessness 

 of such conceptions as explanations; much has been 

 written in their favor, and the only truthful statement 

 possible is that there is no evidence for their existence. 

 The important contribution is the experimental evidence 

 showing that the symmetries and patterns in organisms are 

 definitely modifiable as the result of synthetic and other 

 processes which may be carried on under observation, and 

 which achieve definite results. In most instances thus far 

 recorded results are achieved rapidly, and the end is not 

 postponed or approached in a halting, zigzag manner, but 

 the modification is in appearance definite, precise, reminding 

 one of the regular and precise operations seen in chemical 

 and physical processes. 



There is an interesting analogy between the processes 

 which may be carried on in organisms in modifying the 

 symmetries by combining definite characters, and those 

 which may be carried on in crystallography, as for example, 

 where certain impurities may be introduced into the crystal- 

 lized form and may definitely alter the attributes of the 

 crystal, such as shape, color, hardness, specific gravity, 

 etc. That the parallel is an exact one there is no evidence, 

 but it is at least suggestive in that both the results occur 

 with sharp alternativeness which is so characteristic of 

 chemical and physical operations. 



It does not seem probable that germinal modifications 

 in form and symmetry arise through the changes in particu- 

 lar chemical constituents within the germ cell, as, for 

 example, a particular katalytic agent, or the rearrangement 

 of the side chains in some complex molecule, because, as far 



