550 C. M. Child. 



itself for complete regeneration or else that different influences are 

 localized in different parts of the nervous system. The fact that 

 posterior regeneration is qualitatively complete in the absence of 

 the ganglia while anterior regeneration is not might seem to favor 

 the second alternative. Even if w^e admit that nervous stimuli 

 themselves exert a formative influence there seems to be no good 

 reason for supposing that this influence is due to stimuli of a 

 particular kind differing from other nervous stimuli. Indeed the 

 general consensus of opinion is that in all probability a given 

 nerve cannot transmit qualitatively different stimuli. The ques- 

 tion of the direct formative influence of nervous stimuli has been 

 much debated; in all cases, however, where there is a possibility 

 of the existence of such an influence distinction between it and the 

 formative effect of the functional conditions cannot be made 

 experimentally. 



The second possibility to be considered is the formative effect of 

 functional conditions which plays so important a part in the views 

 of Roux ('95) and others. According to these views the condi- 

 tions connected with functional activity of a part exert an influence 

 which may produce growth or further development of the part. 

 The functional conditions may be various in kind — either physical 

 or chemical. In the organs of movement and support their sup- 

 posed formative influence has been most clearly recognized. If 

 functional conditions exert a formative effect it is clear, as Roux 

 has pointed out, that in those organs whose function is determined 

 by nervous stimuli a formative influence of nervous stimuli will 

 seem to exist since the functional conditions are determined by the 

 existence of a connection between the organs in question and the 

 nervous system. In reality, however, this relation between the 

 nervous system and formative influence is indirect (see Child, '04b, 

 p. 507), since not the nervous stimulus itself but the change 

 brought about in the organ and its environment by function are 

 the essential factors. 



In a paper which has recently appeared Goldstein ('04), after a 

 consideration of the influence of the nervous system upon em- 

 bryonic development and regeneration, reaches the conclusion 

 that the functional stimuli and not the nervous stimuli themselves 



