Paramecium presents several advantages f o r analyzing the effect of radiation on genetic mechanisms. In tlx first place, its sniall size rnakes it suitable for stiidy with less penetrating radiations. Of course, that characteristic is shared with all those organisms discussed this morning. More important however, is the possibility of studying the effects of radiation on both the iiuclear and the cytoplasmic mechanisms of inhe ri tance.
As inany of you know, cytoplasmic inheritance has by now been studied fairly extensively in this organism. The purpose of this paper is to present some results of studies on the effects of radiation on botli types of inheritance, and in PO doing, give you some idea of the possibilities of the material. Unfortunately, very little can be said here about cytoplasmic inheritance even though, in the long rim, this may be the most important aspect f o r study in this organism.
Some work has been done in this laboratory with ultraviolet radiation on the character killer in variety 4 of Paramzeciuw,. This character is dependent, among other things, upon a cytoplasmic factor that has been called kappa, a self-reproducing cytoplasniic entity. As a result of the work of Sonneborn and ' 3111ch of the material in this pape' has been presented in more detailed forln in Genetics, 5 4 : 210-222 and 412-424, 1919. Cominissioii. 'Work performed under contract no. W '7405 Eag-26 for t h e Atollllc Ellerg7