44 



Charles Russell Bardeen 



gests that the hereditary factors contained in spermatozoa might 

 be so altered as to produce specific variation in the individuals 

 springing from ova which they fertilize. 



The effects of altering the normal course of development of 

 vertebrates by electrical, magnetic, chemical or mechanical agents 

 applied to the v^hole organism, have been shov^^n by Dareste,*^ 

 Fere,**® Roux,*^ and many others, to be seldom confined in a 

 specific w^ay to an organ or group of organs, although some 

 organs, like those composing the nervous system, are especially 

 sensitive to all such factors. The experiments with irradiation 

 show that although some tissues are much more susceptible to the 

 rays than others, there are wide differences in the effects of the rays 

 on different individuals. 



In conclusion, I desire to express my thanks to my colleague, 

 Professor B.W. Snow, for the use of the Roentgen ray apparatus 

 belonging to the Department of Physics, and for his aid in con- 

 ducting the exposures. 



EXPLANATION OF PLATES I to V. 



On these plates there are represented outlines of the external forms and transverse sections through 

 the body of one control and five experiment larvae. Descriptions of the larvae represented are to be 

 found in the text as follows: 



Plate I, p. 21 Plate IV— A, p. 31 



Plate II, p. 24 Plate IV— B, p. 37 



Plate III, p. 27 Plate V, p. 35 



**Dareste: Recherches sur la production artificielle des monstruosites. Paris i8qi. 



"'Fere: Coraptes Rendus de la Societe de Biologic, 1893-1905 



*"Roux: Gesammelte Abhandlungen iiber Entv/icklungsmechanik der Organismen, 1895. 



