424 CHARLES RUSSELL BARDEEN 



tance to the X rays exhibited by unicellular organisms seems to 

 indicate that simple reproductive morphogenesis is not readily 

 disturbed by irradiation. Even conjugating paramoecia seem 

 to be in no way disturbed by such exposure and the subsequent 

 offspring appear to be perfectly normal. If morphogenic deter- 

 minants in these forms are injured by the rays they can apparently 

 be, in most instances, repaired. The relatively stable condition 

 of the cytoplasm, which in large part is carried over nearly 

 unchanged from the parent to daughter cells doubtless plays a 

 part in maintaining the general morphogenic stability. 



Differential morphogenesis, cell multiplication accompanied 

 by specific change of organization, is readily influenced by irrad- 

 iation both in plants and animals. Thus Koernicke ('04-05'), and 

 others have found that sufficient exposures to X rays or radium 

 may check the growth of germinating seeds. Tuilleminot ('09), 

 has shown that while there may be a slight germination of seeds 

 exposed to X rays or radium the latter cannot take the place of 

 sun-rays. Immediately after exposure development may be 

 quickened but this is followed later by retardation and abnor- 

 mality or even inhibition of development. Fertilized eggs in 

 the early stages of development are, in all animal species studied, 

 very susceptible to the X rays, although the eggs of some species 

 are apparently somewhat more susceptible than those .of other 

 species. Thus Perthes on exposing the eggs of Ascaris mega- 

 locephala to the X rays found they give rise to irregular masses 

 of cells or to abnormal embryos. Oilman and Baetjer showed 

 that exposure to the X rays causes abnormal development in 

 amphibian and avian eggs and Schafer and G. Bohn obtained 

 similar results by exposing amphibian and reptilian eggs to radium. 

 Tur has found that exposure of the eggs of the snail Philine 

 aperta to radium gives rise to very abnormal larvae. The experi- 

 ments of Bergonie and Tribondeau indicate that mammalian 

 eggs are susceptible to the X rays. 



In the adult mammal those tissues in which differential 

 morphogenesis is constant are those which are most susceptible 

 to the rays. Thus the epidermis, the bone marrow and the gen- 

 erative epithelium of the testicle are all highly susceptible. The 



