GILBERT M. SMITH 3^1 



he found that a mixture of three parts precursor and one part end 

 substance made female cells sexually functional, and that one part 

 precursor and three parts end substance made male cells functional. 

 Mixtures in the ratio of i:i, 2:2, 4:1, and other ratios were without 

 effect on either male or female cells of this species. Later Moewus 

 (10,12) found that the ratios are not the same for all members of the 

 eiigametos series. According to the species or variety the ratio between 

 precursor and end substance necessary to make female gametes sexually 

 functional may be 95:5, 85:15, 75:25, or 65:35. In this series male 

 cells are, respectively, made functional in mixtures of precursor and 

 end substance in the ratio of 5:95, 15:85, 25:75, and 35:65. For each 

 member of the series the ratio for female cells is the reciprocal of that 

 for male cells: that is, 95:5 and 5:95, 85:15 and 15:85, 75:25 and 25:75, 

 65:35 and 35:65. 



Moewus' studies on behavior of cells in light of various wave lengths 

 and in darkness show that sexual substances present in members of the 

 eiigametos group are formed in light and disappear shortly after removal 

 from light. Disappearance of sexual substances of the eiigametos group 

 may be due to a breakdown in the absence of light but this seems im- 

 probable because certain other species do not have a loss of sexual 

 substances when transferred to darkness (see p. 325). It seems more 

 probable that sexual substances formed in hght by members of the 

 eiigametos group have the substances diffusing out from the cells almost 

 as rapidly as they are formed. Since there is no new formation of sexual 

 substances after transfer to darkness and outward diffusion of sexual 

 substances continues after this transfer, the cells soon reach a state 

 where they do not contain a sufficient concentration of sexual substances 

 to cause gametic union. 



The climax of work on sexual substances of the eiigametos group came 

 with the demonstration that they are all formed by degradation of the 

 carotinoid pigment, protocrocin (5,6). A molecule of protocrocin breaks 

 down into two molecules of picrocrocin and one of crocin (Table i). 

 Each of the two molecules of the carotinoid picrocrocin breaks down 

 into a molecule of glucose and a molecule of the carotinoid safranol. 

 The molecule of crocin breaks down into two molecules of the sugar 

 gentiobiose and one molecule of aV-crocetin dimethyl ester which, in 

 time, becomes transformed into /ra/z^-crocetin dimethyl ester. Genetic 

 analysis by Kuhn and Moewus (4) and by Moewus (14) has shown that 



