682 SEXUALITY 



Further, the grades of reaction shown in Table 10 are presumably indices 

 of the magnitude of sex tension between the gametes. Difference of sex 

 always results in a grade 3 reaction, except between gametes of the 

 lowest valence. When alike in sex, a difference of 2 in valence is re- 

 quired for a grade 1 reaction and a difference of 3 for a grade 2 reaction. 



Certain features of Moewus's interpretation are of special interest: 

 ( 1 ) his reduction of what appeared superficially to be many interbreed- 

 ing sexes to but two, assumed to be qualitatively diverse; (2) his iden- 

 tification of these two sexes with male and female; (3) his distinction 

 between unions resulting from (qualitative) difference in sex and those 

 resulting from (quantitative) difference in sex valence. The evidence 

 and reasoning involved in these views is set forth in the following. 



The original basis for holding that only two sexes are present in each 

 interbreeding system appears to be partly that the sexes were discovered 

 in pairs. For example, in the paradoxa-pseudoparadoxa group of species 

 (Table 7), Moewus found the two sexes here called A and F in C. 

 paradoxa, B and E in the race of C. pseudoparadoxa from Coimbra, and 

 C and D in the race from Giessen. Similar pairs of sexes were found in 

 the other group of species: in C. braunii, G and O; in C. dresdensis, 

 H and N; in C. eugametos f. typica, H and N; in C. eugametos f. sim- 

 plex, J and M; in C. eugametos f. subheteroica and f. synoica, K and L 

 in each. Only in C. paupera did an exception appear; the six types H, J, 

 K, L, M, and N were all found together in a single natural source. 



From this point on, it appears to be simply assumed that the two sexes 

 in one race are qualitatively the same as the two in any other race with 

 which it can interbreed. If this assumption be accepted, then the remain- 

 ing interpretation follows naturally. For example, if in C. paradoxa 

 (Table 7) the two sexes A and F are designated -f- and — respectively, 

 then in the Coimbra race of C. pseudoparadoxa B must be -|- and E — , 

 for B copulates with F ( — ), not with A {-\-)\ and E copulates with 

 A (-j-) not with F ( — ) . Similarly, C and D in the Giessen race are -j- 

 and — respectively. This is clear from their mating relations with B and 

 E. The exceptional copulations between like-sexed gametes (A-|- with 

 C-f- and D — with F — ) are interpreted as follows: A and C must both 

 be the same sex (-j-) because of the mating relations set forth above; 

 yet they must also be unlike in some sexual way, for they copulate with 

 each other, though neither will copulate with others like itself; hence 



