72 The Biochemistry of Semen 



and alkaloids; in a few instances, some of these substances have 

 actually been claimed to occur in the archegonia (Pfeffer, 1884; 

 Shibata, 1911). Bracken spermatozoa are attracted by the cis but 

 not the trans, configuration of organic acids; thus, they can be 

 shown to move towards maleic but not fumaric, and towards citra- 

 conic but not mesaconic, acid (Rothschild, 1952). Several organic 

 compounds, including some simple hydrocarbons, ethers and esters, 

 have been shown to possess chemotropic activity for the sperm of 

 certain Fucaceae (Cook, Elvidge and Heilbron, 1948; Cook and 

 Elvidge, 1951). 



Cross-poUination between two flowering plants of Forsythia is 

 brought about by an exchange, followed by enzymic breakdown, of 

 two glycosides of the natural flavonol pigment quercetin, carried 

 with the pollen, namely rutin (quercetin rutinoside) and quercitrin 

 (quercetin rhamnoside) (Kuhn and Low, 1949; Moewus, 1950). 

 Plants also provide several instances of difierential distribution of 

 pigments in the male and female gametes. Among the fungi, the 

 small motile male gamete of some species of Allomyces is distin- 

 guished from the larger female gamete by the presence of an orange- 

 coloured globule in which Emerson and Fox (1940) have found 

 y-carotene along with traces of isomers. In the family Fucaceae, 

 chemical resolution of the pigments from the male and female 

 exudates of several species has shown that the predominant colour- 

 ing matter of the orange-coloured male gametes consists of /^-caro- 

 tene, whereas the olive-green pigmented eggs contain chlorophyll 

 and fucoxanthin (Carter, Cross, Heilbron and Jones, 1948). The 

 participation of carotenoids in the reproduction of algae is indi- 

 cated by studies on the unicellular flagellate alga, Chlamydomonas, 

 where picrocrocin, crocin, and cis-trans-crocQtm dimethyl esters 

 have been shown to play a role in the conjugation of the male and 

 female gametes as well as in sex determination (Kuhn, Moewus and 

 Jerchel, 1938; Kuhn and Moewus, 1940). 



In animals, the position of carotenoids as sperm-active sub- 

 stances remains uncertain, but there is the significant fact that 

 remarkably large amounts of carotenoid pigments occur in male 

 gonads and accessory glands of reproduction of many animals, 

 including mammals (Goodwin, 1950). The importance of vitamin A 

 and carotene in developing and maintaining the normal germinal 



