154 The Science of Life. 



that " the microcosm of the ontogenetic tree is a reflec- 

 tion of the macrocosm of the genealogical tree ", is 

 to express a marvellous generalization, to the dangers 

 of which we have already referred. What we wish to 

 understand is, as Hallez expresses it, how the proto- 

 plasm is, at each stage, the architect as well as the 

 material of its own development. The metaphors of 

 memory and recapitulation suggest that the developing 

 organism has somehow a feeling for history, or that the 

 dead hand of the past is literally upon the present, while 

 our aim must be to get beyond mere phrases, and to 

 understand the chemical and physical conditions which, 

 more or less modified in the course of history, must still 

 be present to rule each step in the development. 



There can be no doubt that, in the modern theory of 

 continuity, there is found the reconciliation between 

 those who maintain that the likeness of offspring to 

 parent is due to the presence of similar conditions, and 

 those who are satisfied in referring the resemblance 

 simply to "heredity". That there is similar material 

 to start with is one half of the truth; that there are 

 similar conditions throughout the development is the 

 other. 



The third problem, which we stated at the outset, 

 concerns the inheritance of acquired characters. It is 

 inheritance we ^ known that many organisms in the 

 of^Acqu^ed course of their individual life are affected by 



aracters. environmental influences, or by use and dis- 

 use of their organs. Thus there result what are con- 

 veniently called "modifications" environmental and 

 functional changes in the body of the individual organ- 

 ism. The question is, whether these may be transmitted 

 to the offspring by the parent which acquires them. 

 Two cautions may be noted in starting: (i) No natural- 

 ist doubts the inheritance of constitutional or organismal 

 variations. These may be reasonably traced back to 

 the fertilized egg-cell. But what is involved in the 

 fertilized egg-cell may also be by hypothesis involved 

 in the germ-cells which give rise to the next genera- 

 tion. There is no argument on this fact; the present 

 scepticism relates to functional and environmental 



