SUSCEPTIBILITY OF AMPHIBIAN OVA TO X-RAYS 421 



repeatedly exposed to the X rays continued to react normally to 

 light, to mechanical and chemical (food) stimuli. Tadpoles 

 repeatedly exposed show no direct impairment of movement. 

 On the other hand Barratt ('10) has recently found that under a 

 disc of radium bromide the skin of the rabbit after two and a 

 half hours exposure becomes pale while about the margin of the 

 disc a circle of pigment is formed. This probably indicates that 

 pigment carrying cells are stimulated to movement by irradi- 

 ation. Casemir ('10) described a cessation of nuclear and cell 

 division in germinating Vicia faba after two and a half hours 

 exposure to the Roentgen rays. 



The metabolic activities of protoplasm cannot well be directly 

 followed. Since active life cannot persist without constant meta- 

 bolism and since exposure to the rays does not as a rule make its 

 effects visible for some time after exposure, it seems fair to con- 

 clude that the simpler metabolic functions are not immediately 

 affected by the X rays. In paramccea exposed for twelve hours 

 to the rays I have found no apparent disturbance of metabolism 

 either during or subsequent to the exposure. M. Zuelzer found 

 much variation in susceptibility to radium in different species 

 of protozoa, when observed under the microscope during expo- 

 sure. In those showing direct injury the nucleus appeared affect- 

 ed before the cytoplasm. Planarians repeatedly exposed to the 

 X rays subsequently die (usually about a month after the first 

 severe exposure). The first effects are seen in the region of the 

 head in which there is a gradual degeneration, apparently in part 

 parasitic in nature. It is uncertain to what extent these effects 

 are to be attributed to interference of the simpler metabolic 

 activities but it seems likely that they are to be attributed chief y 

 to interference with those morphogenic activities which have to 

 do with the restitution of worn or injured parts. In mammals 

 Lepine and Boulud have described an increased amylasis after 

 exposure of the pancreas to the X rays, and in the liver and blcod 

 after moderate exposure an increased glycogenesis and glycolysis. 

 After prolonged exposure both are diminished. Bearmann and 

 Linser have described an increased elimination of nitrogen after 

 severe exposure to the X rays. Irradiation has been used sue- 



