488 Physiology 



successive exposures may interrupt fission of P. caudatuin to form chains 

 of several individuals (201). The ultraviolet action spectrum for Para- 

 meciiun has been described by Giese (154). 



Certain morphological effects are to be expected. Liquefaction of the 

 cortex in A^noeha diibia and A. proteus is followed by temporary lique- 

 faction of the endoplasm and then, after heavier dosage, by gelation of 

 the endoplasm (196). Comparable changes occur in Spirostomiim am- 

 biguuni (524). After short exposures the endoplasm becomes fluid and 

 cyclosis is accelerated, while prolonged exposure causes gradual increase 

 in viscosity, and finally coagulation and vacuolation. Locomotion is ac- 

 celerated at first, but ceases as lethal dosage is approached. Fragmentation 

 of the macronuclear chain is common. The cortex eventually ruptures 

 after lethal exposure. Vacuolation and cytolysis, following immobiliza- 

 tion, also have been described in 11 other species of ciliates (151, 157). 

 Cytolysis has not been observed in Peranema trichophorum , although 

 immobilization, distortion of the body and coagulation of the endoplasm 

 are characteristic effects (52.S). Euglena gracilis disintegrates after heavy 

 dosage with quartz ultraviolet, but green flagellates are less sensitive than 

 colorless strains of the species (250). 



Beyond the ultraviolet, the X-ray spectrum extends into the region of 

 gamma-rays emitted by radium, decreasing wave length being correlated 

 with increasing power of penetration ("hardness"). Of the radium ema- 

 nations (alpha, beta, and gamma rays), alpha-rays are softest and gamma- 

 rays hardest. X-rays produced at 1,000 kv or more extend into the 

 gamma-ray region. 



The morphological effects of X-rays and radium are similar to those of 

 ultraviolet. Movement of Paramecium (95) and Colpidijwi (76) is first 

 accelerated and then retarded in lethal exposure to X-rays, and amoeboid 

 movement is similarly affected by radium (435). Vacuolation of the cyto- 

 plasm, upon exposure to radium, has been noted in Amoeba diploidea 

 (584), A. vahlkampfia (435), Entamoeba histolytica (409), and Spiro- 

 stomwn aynbiguum. (496), and the effect of X-rays on Euplotes taylori is 

 similar (38). Cytolysis of Paramecium (95), although not of Peranema 

 trichophorum (523), is caused by lethal dosage with X-rays, and lethal 

 exposure to radium induces cytolysis of Spirostomum ambiguum (496). 

 Heavy dosage with alpha rays (polonium source) causes immobilization 

 and cytolysis of Polytoma uvella. Lighter dosage may be followed by fis- 

 sion, but the daughter flagellates undergo cytolysis (206). Sublethal ex- 

 posure of Eudorina elegans to radium induces deformed daughter colonies 

 containing less than the normal number of flagellates (169). Unusually 

 large organisms, resulting from continued growth but retarded fission, 

 occur in Colpidium colpoda after exposure to X-rays (76), and in Bodo 

 caudatus (485, 487) and Entamoeba histolytica (409) after exposure to 

 radium. The sensitivity of Paramecium to X-rays is increased by pre- 



