VARIATION AND HEREDITY 169 



pected with present methods. Unless further progress can be made 

 in cytological studies, the burden of attack must fall all the more 

 heavily on purely genetic methods. On the basis of genetic work 

 alone, we are led to conclude that the usual Mendelian situation, 

 modified by certain details pecuHar to the organism, probably 

 exists in Paramecium. In agreement with Pascher, we find the 

 fundamental patterns of protozoan and metazoan genetics to be 

 very nearly the same." 



De Garis produced monsters in P. caudatum by exposing 

 dividing individuals either to low temperature or cyanide vapor, 

 which were L-shaped and one or both components divided usually 

 on the second or third day, producing free individuals. The genet- 

 ic constitution of progeny was not altered by the experience of 

 monster formation. By bringing about conjugation between 

 monsters and free individuals which differed in fission rate and 

 body length, De Garis produced hereditary diverse races from 

 the two lines. On the other hand, the conjugation between P. 

 aurelia and double monster of P. caudatum was found to have 

 lethal effects on both ciliates, as the former species degenerated 

 ("cloudy swelling") and died on the second or third day after 

 conjugation, while the latter species manifested hyaline degenera- 

 tion and died on the second to twelfth day after conjugation. 



The discovery of sex reaction types in Paramecium aurelia 

 and P. bursaria, as was stated in the last chapter, and further 

 researches along this line, will, it is hoped, throw a clearer light 

 on various genetical problems in Protozoa. 



References 



Calkins, G. N, 1924 Urole-ptus mohilis. V. Jour. Exp. Zool., 



Vol. 41. 

 De Garis, C. F. 1934 Genetic results expressed by fission rates 



following conjugation between double monsters and free 



individuals of Paramecium caudatum. Amer. Nat., Vol. 68. 

 1935 Lethal effects of conjugation between Paramecium 



aurelia and double monsters of P. caudatum. Ibid., Vol.69. 

 Jennings, H. S. 1909 Heredity and variation in the simplest 



organisms. Ibid., Vol. 43. 

 1916 Heredity, variation and the results of selection in 



the uniparental reproduction of Difflugia corona. Genetics, 



Vol. 1. 



1929 Genetics of the Protozoa. Bibliographia Genetica, 



Vol. 5. 



