Abnormal Development of Toad Ova 43 



cesses. In one instance marked ingrowth of processes from the 

 ectoderm occurred. 



The cells of the tissues appear for the most part clear in outline. 

 Many of the cells of the central nervous system seem to have under- 

 gone a pigmentary degeneration. Numerous cells in most of the 

 tissues show mitotic figures. I have been unable satisfactorily to 

 determine whether or not there are abnormalities in these figures. 

 There is an abnormal number of cells with two or more nuclei. 

 A striking feature of the experiment embryos is the irregular dis- 

 tribution of the pigment cells. They are much more irregularly 

 distributed through the tissues than in the normal embryos. 



There is a striking resemblance between tadpoles which de- 

 velop from ova fertilized by sperm exposed to the Roentgen rays 

 and the tadpoles exposed directly to radium irradiation by Schaper*^ 

 This shows clearly that injuries produced in nuclei may be carried 

 through many generations of cells in an individual and finally 

 give rise to deformities corresponding with those due to direct 

 irradiation. Bohn^- found that the rays of radium rapidly enfeeble 

 or kill the sperm of strongylocentrotus lividus, but that the eggs 

 appear more fertile after exposure. He does not describe the effect 

 of exposure of the germ cells on subsequent development. 



Herbst*^ found by treating the sperm of sea-urchins with fresh 

 water, alkalies and potassium-free salt water and then fertilizing 

 ova of a different species with the sperm thus injured that the ova 

 sometimes developed as if injured but that there was no evidence 

 that the specific hereditary factors transmitted by the spermatozoa 

 were altered. Further studies are necessary to determine if the 

 hereditary factors carried by the sperm may be specifically influ- 

 enced by irradiation. D. T. Macdougal^* has shown that in some 

 plants mutations may be produced by injecting radium prepara- 

 tions, sugar solutions and solutions of calcium nitrate and of 

 zinc sulphate into the ovaries. This most important work sug- 



*'Schaper: Anat. Anzeiger, xxv, p. 298, 1904. Levy: Archiv f. Entwicklungsmechanik,xxi,p. 

 130, 1906. 



*^G. Bohn: Comptes Rendus de I'Acad. des Sciences, Paris, cxxxv, p. 1012, 1085, '9°3" 

 ^'Herbst: Archiv fiir Entwicklunsmechanik der Organismen, xxi, p. 293, 1906. 

 *'MacDougaI: The Popular Science Monthly, September, 1906, p. 16. 



