EFFECT OF RADIUM ON FERTILIZATION 87 



one hour to three days, found that the most noticeable effect was 

 on the nucleus of the cells, the protoplasm apparently undergoing 

 no change. The chromatin was clumped together, and in some 

 cases formed a homogeneous ball. He also found in the tetrad 

 cells a great number of small nuclei, and many extra-nuclear 

 nucleol'. 



Guilleminot ('08) found similar changes. With intense ra- 

 diation (200 mg. of the pure bromide) the nucleus of the pollen 

 grain lost all power of division after the fertilization of the ovule. 

 With weaker stimulus the resulting embryo was small and ab- 

 normal in various respects. If the stimulus is applied during 

 fertilization the injurious effect appears early in development, 

 and the plant is unable to repair the injury. If the adult tissue 

 of the plant is exposed, very little effect can be noted. 



Experiments on the effect of radiations on the germ cells and 

 on the fertilized egg have been carried on by numerous observers. 

 The first of these was Bohn ('03) who used the frog and sea- 

 urchin as the basis of investigations. In general he found that 

 the radiations produce a retarding and injurious effect on the 

 early development of both of these forms. On exposing sea- 

 urchin sperm he found that they very soon lost their motility and 

 failed to fertilize the eggs, a fact not borne out by the experiments 

 of G. Hertwig in the case of Parechinus miliaris, or by my own 

 on Arbacia punctulata. 



Perthes ('04) has described similar effects of radiation on the 

 fertilized eggs of Ascaris megalocephala. Schaper ('04) and 

 Levy ('06) have described the abnormal larvae arising from the 

 radiated, fertilized frog's egg. The abnormalities consisted in 

 the peculiar shape of the larvae, and the pathological condition of 

 the nervous system. The vascular system also was much injured. 

 Schaper believed that the abnormalities in the embryo were 

 due in a large measure to the destructive action of radium radia- 

 tions on the yolk, the lecithin being destroyed through the ioniz- 

 ing effect of the radiations. This theory, first proposed by 

 Schwarz ('03), will be discussed later. 



Bardeen ('11) has found that A^ rays (which are similar to the 

 gamma rays of radium) produce a marked effect on both eggs and 

 sperm cells of frogs so that they give rise to abnormalities. The 



