192 Charles Russell Bardeen, M. D. 



Our first experiments were upon worms from each of which 

 the anterior region of the body was removed Immediately before 

 the first exposure. The cut edges became closed In by muscular 

 contraction and the extension of epithelium In the usual manner. 

 For some days there was a slight production of new tissue near 

 the cut surfaces, but this soon ceased. No new heads were pro- 

 duced and no new pharynges. In one specimen of P. maculata, 

 however, an Imperfect eye was regenerated on the left side at the 

 junction of the old tissue with the new, and a very small eye-spot 

 appeared on the right side, but the anterior end of the piece 

 at no time assumed the normal shape of a head. The specimens 

 were subjected to thirteen exposures. All died between the twen- 

 tieth and twenty-second days after the first exposure. Control 

 specimens regenerated In the usual manner. A "tail-piece" of 

 P. maculata had become a worm of perfect form and proportions 

 on the fifteenth day after the operation, and a "tail-piece" of 

 P. lugiibris had regenerated a well proportioned new head and a 

 new pharynx at that time. 



Several experiments were made to test the effect of the 

 rays on uninjured worms. Specimens were exposed from 

 twelve to eighteen times and were then kept under as hy- 

 gienic conditions as possible. Some of these Individuals lived 

 a month after the first exposure. During this period they 

 reacted normally to light, to mechanical and to chemical (food) 

 stimuli. Microscopical preparations made from a few specimens 

 at varying periods after the last exposure showed no marked 

 alterations In the muscular, nervous and Intestinal apparatus. The 

 cutaneous epithelium seemed to be normal except for a few areas 

 where the cells were shorter and broader than usual. The cUIa 

 of the ciliated cells were Intact. In specimens with well-developed 

 genitalia the cells of the testes showed no karyoklnesls. On the 

 contrary most of them seemed to be undergoing a degenerative 

 change. In corresponding control specimens mitosis was most 

 active In these cells. No clear Instances of nuclear degeneration 

 were observed. Death In these specimens resulted from a de- 

 generative process which began In the region of the head and 

 extended slowly back. This degeneration was probably parasytic 



