DOMINANCE IN RECONSTITUTION 341 



the radial nerve remains at the distal cut surface but is isolated from 

 central parts, except for possible lateral connections. Whether the nerv- 

 ous system is essential to regeneration of a complete disk and arms from 

 a single arm in certain starfishes (e.g., Kellogg, 1904) is not known. 



Reconstitution of the bryozoan from a statoblast and of certain ascid- 

 ians from winter buds seems to be essentially development of a new indi- 

 vidual from what is primarily little, if anything, more than a cell aggre- 

 gate; the new nervous system develops in complete isolation from the old. 



The question of nervous influence on regeneration of amphibian ap- 

 pendages has been the object of extensive experiment, and the literature 

 shows marked difference on the conclusions reached, although most au- 

 thors find some nervous influence.^ Some find merely retardation of re- 

 generation and failure to attain normal size after ehmination of regions of 

 the spinal cord innervating the leg, and it has been repeatedly suggested 

 that this effect is due merely to lack of function in the regenerating leg. 

 However, the possibility of some degree of innervation by other than the 

 normal nerves has not always been excluded. Goldfarb denies nervous in- 

 fluence. Walter finds that absence of motor innervation is without eft'ect 

 but holds, as does Locatelli, that regeneration does not take place in ab- 

 sence of nervous connection and suggests that connection with spinal 

 ganglia is essential. According to Weiss, there is proliferation but no true 

 regeneration in absence of nervous connection. He regards the nervous 

 influence not as formative or determinative but as a tonic excitation from 

 the sympathetic system. Schotte's experiments lead him to a similar con- 

 clusion. Hamburger, working with anura, finds legs normal in form but 

 of small size, regenerated in apparent complete absence of innervation, 

 but admits that the possibihty of sympathetic innervation is not ab- 

 solutely excluded. 



At present there is general agreement that absence of motor innerva- 

 tion does not prevent leg regeneration but may retard or prevent growth 

 to full size through absence of function. The experiments of Weiss and 

 Schotte indicate the necessity of sympathetic innervation, and these and 

 various other authors agree that the nervous influence is not formative. 

 Apparently it is a factor in determining and maintaining the physiologi- 

 cal state, the level of physiological activity, of the cefls which makes pos- 

 sible a sufficient activation following section to bring about the degree of 

 physiological isolation necessary for establishment of a new dominance 



8 Goldstein, 1904; Wintrebert, 1904; Goldfarb, 1909; Wolff, 1910; Walter, 1911; Weiss, 

 1925a, 1930, p. 124; Schotte, 19266, c; Brunst, 1927; Hamburger, 1928; Locatelli, 1929, and 

 literature cited by these authors. 



