676 SEXUALITY 



ganisms that produce it, by means of filtration and centrifugation, and 

 found it to have two striking effects. Gametes grown in the dark are 

 incapable of copulating, but treatment with the sex stuff from a ripe 

 culture of gametes of the same sex rendered them capable of copulation. 

 It will be recalled that activation of non-reactive gametes by filtrates from 

 cultures of reactive gametes has previously been referred to (pp. 668- 

 669) as the method employed in activating the peculiar gametes of the 

 Giessen race of C. pseudoparaJoxa, which are always normally nonreac- 

 tive. This situation differs from most of the others described by Moewus 

 in that activation is here brought about by the sex stuff from gametes of 

 a different sex. Reference to page 672 and Table 7 will show that the 

 sex stuff from sexes B and E were used to activate gametes of sexes C 

 and D respectively. Similarly Moewus (1934) states that filtrates from 

 sex K can activate gametes of sex H. This raises the question of how wide 

 a range of sexes can be activated by sex stuffs from any one sex. Moewus 

 (1939a), in a discussion of those sexes which I have designated G to 

 O, states that each sex can be activated by filtrates only when they are 

 derived from active gametes of the same sex. The earlier results with C. 

 pseudoparaJoxa and C. eugametos (Hartmann, 1934; Moewus, 1934) 

 do not agree with this generalization. 



The second effect is observed when reactive gametes of one sex are 

 added to sex stuffs obtained from gametes of certain other sexes. The 

 introduced gametes form groups or clusters as if they were about to 

 copulate, but eventually the clusters disintegrate without copulation tak- 

 ing place. This happens when reactive gametes of one sex are added to 

 sex stuffs from filtrates of reactive gametes of the other sex in the same 

 race, as, for example, when gametes of sex J are added to filtrates from 

 gametes of sex M, for sexes J and M are the two found in C. eugametos 

 i. simplex. Whether similar effects of one sex stuff are producible on 

 more than one other sex is not stated. The important point here is that 

 sex stuffs can induce a sex reaction between cells alike in sex, but cannot 

 induce them to copulate with each other. This indicates that there are 

 two distinct processes in the sex act: the agglutinative sex reaction, and 

 the actual fusion of cells and nuclei. The sex stuffs function in the for- 

 mer but not in the latter process. The existence of sex differences with- 

 out sex stuffs (or with sex stuffs in ineffective concentrations) is also 

 shown by the gametes of C. pseudoparadoxa from Giessen (see p. 668 



