32 Heredity and Environment 



opment is well established. To what extent structures may modify 

 functions or functions structures, in the course of development, 

 is a problem which has been much discussed, and upon the answer 

 to it depends the fate of certain important theories, for example 

 Lamarckism; but this problem can be solved only by thorough- 

 going experimental and analytical work. In the meantime it seems 

 safe to conclude that living structures and functions are insep- 

 arable and that anything which modifies one of these must of 

 necessity modify the other also; they are merely different aspects 

 of organization, and are dealt with separately by the morpholo- 

 gists and physiologists only as a matter of convenience. At the 

 same time there can be no doubt that minute changes of function 

 can frequently be detected where no corresponding change of 

 structure can be seen, but this shows only that physiological tests 

 may be more delicate than morphological ones. In certain lines 

 of modern biological work such as bacteriology, cytology, and ge- 

 netics, many functional distinctions are recognizable between or- 

 ganisms that are morphologically indistinguishable. But this does 

 not signify that functional changes precede structural ones, but 

 only that the latter are more difficult to see than the former. For 

 every change of function it is probable that an "unlimited micro- 

 scopist" could discover a corresponding change of structure. 



II. DEVELOPMENT OF THE MIND 



The development of the mind parallels that of the body : what- 

 ever the ultimate relations of the mind and body may be, there 

 can be no reasonable doubt that the two develop together from 

 the germ. It is a curious fact that many people who are seriously 

 disturbed by scientific teachings as to the evolution or gradual de- 

 velopment of the. human race accept with equanimity the universal 

 observation as to the development of the human individual, 

 mind as well as body. The animal ancestry of the race is surely 

 no more disturbing to philosophical and religious beliefs than the 

 germinal origin of the individual, and yet the latter is a fact of 



