September 3, 1915] 



SCIENCE 



293 



find no ground for the lecithin theory, but 

 interprets her facts from the contrary view- 

 point. The effect of radium upon Ascaris 

 eggs has been reinvestigated by Payne^" who 

 confirms the results just given. 



Giinther Hertwig, following the lead of 

 his father, in his various studies set up four 

 series of experiments, the A, B, C and D 

 series. In the A series, eggs were radiated 

 in the two-cell stage, or after fertilization; 

 in the B series, sperm were radiated and 

 then used to fertilize normal eggs ; in the C 

 series, eggs were radiated and then fertil- 

 ized by normal sperm ; in the D series, both 

 eggs and sperm were radiated before fer- 

 tilization. The experiments described in 

 his first paper were on the frog's egg. He 

 found that in the C series (normal sperm 

 by radiated eggs) the injury increases 

 with the duration of the radiation up to a 

 maximum, and from there on decreases 

 again as the radiation is prolonged. Only 

 the radiated nuclei show the effects, and 

 there is no evidence for the hypothesis that 

 yolk which contains lecithin is being broken 

 down. The injury is greatest on young 

 tissue and on tissues which are to be highly 

 specialized; it is productive of manifold 

 disturbances of the developmental processes. 

 In the frog development is possible with 

 only a haploid nucleus, that is, only the 

 half of the nucleus derived from one parent. 

 "Where the injury is severe to either the egg 

 or sperm nucleus, the other is able to carry 

 on the development, and in fact there is less 

 interference with the regular course than 

 in the case where both nuclei are injured 

 slightly and both take part in the process, 

 for here the injured half is no longer a 

 factor ; it is able only to stimulate develop- 

 ment and then is eliminated from the proc- 

 ess. In other words from the standpoint of 



10 Payne, F., " A Study of the Effects of Eadium 

 upon the Eggs of Ascaris megalocepJiala univalens, ' ' 

 Bcmx ArcUv., XXXVI., 1913. 



heredity, this is a case of parthenogenesis. 

 For the spermatozoon always has two func- 

 tions to perform: it must initiate develop- 

 ment, and it must carry the inheritance 

 from the male line. In this case only the 

 first function is accomplished, and parthe- 

 nogenesis is the virtual result, the male 

 pronucleus being eliminated from develop- 

 ment by failing to unite with the female 

 pronucleus. This result is important as evi- 

 dence that the nucleus is the bearer of the 

 inheritance substance and that in the begin- 

 ning of development male and female 

 nuclei are of equal significance. 



Subsequently Giinther Hertwig per- 

 formed a similar set of experiments on the 

 eggs of the sea urchin. Here he was able 

 to work out the eytological details of the 

 process and to establish firmly his view just 

 stated, that the eggs after intense radia- 

 tion really undergo parthenogenetic devel- 

 opment. This is the most important point 

 of his contribution, although he presents 

 much evidence for the biological hypothesis. 



A great many other experiments have 

 been carried on in Hertwig 's laboratory at 

 Berlin, and all of them contribute to the 

 same conclusions. The principles already 

 discussed are the most important ones 

 brought out, and they are supported by a 

 large amount of evidence; many data also 

 have been gathered from these experiments 

 which are valuable from the standpoint of 

 teratology. This, of course, is incidental to 

 the evidence for the biological hypothesis. 



In America, although much attention has 

 been given to the medical aspects of radio- 

 activity, very little work on the biological 

 phases of the problem has been attempted. 

 Bardeen^^ has carried out systematic ex- 



11 Bardeen, C. R., ' ' Abnormal Development of 

 Toad Ova Fertilized by Spermatozoa Exposed to 

 Rontgen Eays, " Jour. Exp. Zool., TV., 1908. 

 "Variations in Susceptibility of Amphibian Ova 

 to the X-rays at Different Stages of Develop- 

 ment," Anat. Secord, III., 1909. "Further Stud- 



