ACTION OF X-RAYS UPON PARAMCECIA. 63 



during a continuous period of thirty minutes. At the expiration 

 of this exposure the motility of the organisms had become 

 appreciably slower. No changes, however, could be observed 

 either in the character of the cytoplasm or of the nucleus under 

 a magnification of 400 diameters. On May 7, 1916, the observa- 

 tion was made at 2:30 P.M. that a few of these paramoecia were 

 still active though they had lost a great deal of the rapidity of 

 action of their cilia. The majority were motionless and rested 

 upon the bottom of the glass. These had assumed a spherical 

 shape, while in them there could be detected unmistakable evi- 

 dences of degeneration of both nuclear and cytoplasmic material. 

 In the unstained specimens these facts were demonstrated 

 through a loss of their translucent character and by the granular 

 appearance of the protoplasm. Series B consisted of six cultures 

 of paramoecia which were rayed under conditions similar to 

 those of series A for a period of twenty-six consecutive minutes. 

 At the termination of the exposure all of the paramoecia were 

 vigorously active. There was no indication of the slowing down 

 of ciliary motion. A study of the specimens forty-eight hours 

 thereafter demonstrated a still vigorous motility. No dead 

 paramoecia could be found. 



By this method of varying the length of the exposure to the 

 X-ray energy, the other conditions of the experiment remaining 

 constant, it was ascertained that continuous raying during a 

 period varying from thirty to forty minutes was necessary to 

 bring about, upon the day following the raying, a complete 

 sessation of motility and unmistakable evidences of degeneration. 

 It was not possible, however, to cause protoplasmic changes 

 immediately following the raying in either the nucleus or the 

 cytoplasm. These could be made out first only after a twenty- 

 four hour interval after the raying had elapsed. Beyond this 

 no further inquiry was made to ascertain the cytological cause 

 of cessation of motility. Similarly through repeated experi- 

 mentation, it was found that exposures of from ten to twenty 

 minutes duration exercised no effect whatever, either imme- 

 -diately or subsequently, upon either the motility or the vitality 

 of the organisms. A study of these rayed organisms was not 

 conducted, however, throughout a period greater than eight 

 days after the raying. 



