Regeneration in Amphinoma Pacifica, etc. 



99 



Table 2. 



Tables i and 2 establish the fact that at anterior levels the head piece 

 can not regenerate a tail, while the tail piece can regenerate its head. At 

 posterior levels the reverse occurs: the tail piece can not regenerate a head, 

 though the head piece can regenerate a tail. In the median levels both 

 pieces may regenerate their respective missing parts. These preliminary 

 facts concerning the regeneration of Amphinoma, after ordinary amputation, 

 will aid in understanding the behavior of the head and tail pieces after the 

 removal of the nerve-cord as already described. Of the 56 operated head 

 pieces, 29 survived 25 to 30 days, as shown in table 3, which also gives the 

 level amputated and the number that failed to regenerate. 



Table 3. 



operated head pieces 



Survived 



Amputated at one-eighth level . . 



one-fourth level . . 



one-third level . . . 



one-half level .... 



three-fourths level 



These operations were made at anterior levels before it was known that 

 head pieces did not normally regenerate from these parts of the worm. 

 Though regeneration took place readily at posterior levels of control worms, 

 not one operated head piece developed a tail. The experiment appears to 

 demonstrate that, in these instances at least, regeneration had been pre- 

 vented by destroying the nerve-cord near the amputated level. 



I have elsewhere suggested* that regeneration could be prevented and 

 frequently was prevented by various means other than injury to the central 

 nervous system. In the newt Diemictylus, the regeneration of the tail was 

 prevented by plugging the cavity of the spinal column with paraffin. In 

 the salamander Tornier^ prevented the formation of the tail by operating 

 the skin and muscle tissues in a manner to prevent their coordinate de- 

 velopment. In Amphinoma regeneration was prevented not only by injury 

 to the nerve-cord, but by removing the alimentary tract from five or more 

 segments nearest the amputated level. In table 4 the anterior pieces with the 

 alimentary tract so removed are arranged according to the level amputated. 



1 Goldfarb, A. J. The influence of the nervous system in regeneration. Jour. Exp. Zool., vol. 7, 1909. 

 The central nervous system in relation to the phenomenon of regeneration. Arch. f. Entw., vol. 32, 4. 191 1. 



*Tornier, G. Kamp der Gewebe im Regenerat bei Begunstigung der Hautregeneration. Arch. f. Entw,, 

 22, 1906, p. 348. 



