REGENERATION 



431 



the ionization chamber of Failla, in use at the Marine Biological Labora- 

 tory in the summer of 1930. Immediately after irradiation the worms 

 were divided by transverse cutting into pieces approximately 2 mm. in 

 length and checked against controls obtained in the same manner which 

 regenerated normally. In each series the irradiates healed their cut 

 surfaces. In the series exposed to 4000 and to 6000 r there was a slight 

 development of the brain and eyes when the pieces were killed 41 days 



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Fig. 11. — Effect of X-rays upon posterior regeneration of Tuhifex tuhifex as shown by 

 microphotographs of whole mounts. 1, X-rayed worm 7 days after removal of posterior 

 segments; 2, control 7 days after a similar removal; .3, control and X-rayed specimens 

 14 days after such removal; 4, control and X-rayed 21 days after removal; 5, control and 

 X-rayed 30 days after removal. Plane of removal shown by line in each figure. {From 

 Stone, 58.) 



after exposure. In the 8000 r and in the 12,000 r series there was 

 healing and the pieces were normal in appearance, but there was no 

 evidence of regeneration externally when they were killed at 41 days. 

 A preliminary histological examination showed no beginnings of regener- 

 ating organs and an absence of embryonic cells, although other cells 

 appeared normal as seen in the sections. Since the irradiated pieces 

 were in good condition when killed, there was as good reason to believe 

 that death would have resulted eventually from starvation as that it 

 would have resulted from any delayed effects of the irradiation. Com- 

 pletion of this study by Coldwater has been delayed. In view of the 

 general resemblances between the histological factors of regeneration in 

 nemerteans and planarians and the fact that nemertean tissues are 

 perhaps more favorable for such study, its publication in extended form 

 is desirable. 



