SEXUALITY 



695 



Table 13: The System of Breeding Relations in Paranieciuni hmsaria, 

 Data from Jennings, 1939a* 



* The three groups (or varieties) 1, 2, and 3 do not interbreed; conjugation occurs only among 

 the four or eight mating types within each variety. + = conjugation ; — = no conjugation. 



if it mates with A, B, and C, but not with D, it is of mating type D. 

 Five of the seven species of Paramecium found in the United States 

 have been examined for mating types and all have shown them. P. 

 aurelia and P. hursana have already been discussed. In ?. cau datum, 

 Gilman (1939) finds a system of the same kind as found in P. aurelia: 

 six mating types occurring in three groups, with only two interbreeding 

 mating types in each group, and no conjugation between types in dif- 



