492 CHARLES RUSSELL BARDEEN 



The first lot of eggs of Lot B was exposed in the sixteenth to 

 seventeenth hour. It was more susceptible than the eggs of Lot 

 A at this period. This greater susceptibility lasted through the 

 early stages of gastrulation but disappeared toward the end of 

 this period. 



In this connection we may refer to the work of Wintrebert ('06), 

 mentioned above, who found that emanations of radium favor- 

 able to the development of frog larvae would kill eggs in the early 

 stages of development. 



When cell division is increased in rapidity by raising the tem- 

 perature the X rays have more effect than when cell division is 

 reduced in rapidity by lowering the temperature. 



In table C are summarized the internal changes found at differ- 

 ent stages of development after exposing the organism at various 

 periods. In many of the cells of the abnormal organs the nuclei 

 both resting and dividing show marked abnormalities but in 

 other cells they appear nearly normal. At times, however, 

 especially during mitosis very irregular forms are seen. Apparent 

 cases of amitosis are not infrequent. 



BIBLIOGRAPHY 



Ancel, p. and Bouin, P. 1907 Rayons X et les glandes genitales. Presse 

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Baermann and Linser 1904 Tiber die lokale und allgemeine Wirkung der 

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 Miichener med. Wochenschr. Bd. 51, p. 918-994. 



Barratt, J. O. Wakelin 1910 The action of the radiation from radium bromide 

 upon the skin of the ear of the rabbit. 

 Quarterly Jour, of Expt. Physiology vol. 3, p. 261. 



Bardeen, C. R. 1907 Abnormal development of toad ova fertilized by sperma- 

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1909 Variations in susceptibility of amphibian ova to X rays at differ- 

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Bardeen and Baetjer 1904 The inhibitive action of the Roentgen rays on 

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