RADIATION AND ARBACIA GERM CELLS. 457 



of the effects resulting from the separate treatment of either 

 eggs or sperm. (See also G. and P. Hertwig, '13.) The latter 

 authors, by exposing the sperm of frogs, fish, and sea urchins, to 

 the action of chloral hydrate, strychnine nitrate, and methylene 

 blue, were able to obtain delayed cleavage and modified develop- 

 ment. They report, as a result of fertilizing the eggs of Rana 

 esculenta by sperm of Rana fusca, previously treated with chloral 

 hydrate, the appearance of short, cedematous larvse with bent 

 tails (and some with spina bifida) and poorly developed eyes. 

 They further state that sperm may be injured without impair- 

 ment of motility and that the sperm chromatin, although injured, 

 remains in the egg during cleavage. This fact is further sub- 

 stantiated in their work on Strongylocentrotus lividus and Sphx- 

 rechinus granularis; they fail to find evidence of the induced 

 parthenogenesis which others have described. 



A number of experimenters have exposed one or the other sex 

 component to the action of radium or x-rays. Bardeen, '07, '09, 

 modified Amphibian development by exposing sperm and eggs to 

 radium and x-rays. His results indicate a modification of de- 

 velopment of those body regions where growth and complex 

 differentiation are normally most rapid, e.g., neural tube, eyes, 

 nose, and heart, i.e., differential inhibition. Oppermann, -'13, 

 studied the effects of radium radiation on sperm as well as on 

 fertilized eggs of trout. He records defects of the eyes and head 

 and abnormal development of the tail region. G. Hertwig, 'n, 

 '12, '13, found that prolonged exposure of the sperm of frogs 

 and Arbacia to radiation injures the chromatin so that it cannot 

 take part in cell division. When unfertilized frogs' eggs are 

 subjected to radium treatment and are then fertilized by normal 

 sperm, the developing larvae show the greatest modification in 

 the developing sense organs, muscle plates, and blood cells. 

 O. Hertwig, '11, '13, using radium on the germ cells of the frog, 

 and the eggs of Triton was able to obtain differentially modified 

 forms. P. Hertwig, 'u, found that the chromatin in radium- 

 treated Ascaris eggs was affected before the cytoplasm, and that 

 cleavage was delayed and irregular and death appeared early. 

 She also studied the behavior of the chromatin of radium-treated 

 frog sperm, '13, and found that the sperm nucleus took no part 



