WEISMANNISM AND OTHER THEORIES 413 



cule," which is made up of a chain or ring of amino-acid radicles to which 

 side-chains of various kinds may become attached. With regard to 

 individual development it is supposed that "in the ovum there is one 

 common idioplasm of simple type, to which, when distributed in the 

 various cells derived from that ovum, different side-chains become 

 attached, according to the relationships assumed by those cells, so that 

 the cells of different orders are controlled and formed around proto- 

 plasmic or idioplasmic molecules composed of those central rings plus 

 varying series of side-chains" (p. 145). With Driesch it is held that "the 

 structure of the cells in a multicellular organism is a function of their 

 position," since "the position of the cell determines the modification under- 

 gone by its idioplasm." Furthermore, "the greater the change impressed 

 upon the idioplasm of these cells, and the longer that idioplasm is sub- 

 jected to the conditions inducing this change, the more permanently will 

 the daughter cells exhibit the peculiar alteration in the idioplasm, with con- 

 sequent modified structure wherever they find themselves in the economy. 

 We have, in short, to recognize that two orders of forces determine the 

 structure of every cell in the body : (1) the previous influences acting upon 

 its idioplasm and causing it to be of a particular chemical constitution; 

 and (2) the position in which the cell finds itself, and the forces acting 

 momentarily and immediately upon its idioplasm. Or, briefly, these two 

 series of forces are inheritance and environment, and inheritance and 

 environment determine the constitution of the idioplasm and the struc- 

 ture of the cells" (p. 151). 



"In terms of this theory, therefore, inheritance essentially depends 

 upon the chemical constitution of the idioplasm or the life-bearing or 

 biophoric protoplasm of the germ cells, not upon the number of the sepa- 

 rate ids or biophores or ancestral plasms or pangens contained in the idio- 

 plasm; and variation, whether slight and individual, or extensive and 

 leading to the production of new species, is ultimately the expression of 

 modification in the constitution of that idioplasm brought about by envi- 

 ronment. Whereas Weismann's theory lays stress upon relative fixity 

 in the constitution of the idioplasm, this theory admits freely the capacity 

 for change in structure of the same. So long as the surrounding condi- 

 tions are unaltered the idioplasm is unchanged ; alter these conditions and 

 the idioplasm is liable to variation in constitution" (pp. 152-3). 



Adami cites certain calculations of the probable size of inorganic and 

 organic molecules to show that the existence of a system of determinants 

 or other representative particles of the Weismannian type is a physicial 

 impossibility. He also points out that since the idioplasm must increase 

 enormously in bulk by the addition of new material and become repeat- 

 edly subdivided as cells and individuals multiply, there can be no actual 

 continuity of the germ-plasm through countless generations: what is 

 eternal is rather a potential continuity of molecular arrangement and 



