FERTILISATION 197 



presence of some compound containing the (SH) group. Hopkins 

 has recently isolated from the yeast-cell a substance which is 

 undoubtedly closely related, if not identical with this respiratory 

 body of Meyerhof. It proves to be a combination of two ammo- 

 acids, glutamic acid and cystiue, to which Hopkins l has given the 

 name of Glutathione. This dipeptide possesses most remarkable 

 properties in that, in the reduced (SH) form, it can take up 

 molecular oxygen, while in the oxidised (S-S) form so produced it 

 can act as a hydrogen acceptor, and can catalyse oxidations of the 

 Wieland type, in which no activation of oxygen probably takes place, 

 but an activation of hydrogen occurs instead. In the presence of a 

 suitable acceptor the hydrogen is removed and the oxidation of tbe 

 original substance takes place. It can therefore be both reduced 

 and oxidised under the influence of factors known to be present 

 in the tissues themselves. Moreover, it possesses precisely those 

 properties which a co-ferment adapted to an oxidase system would 

 possess, and at present stands entirely in a class by itself. Hopkins 

 has shown that it is present in most living cells, but he could find 

 no trace of it in the hen's egg, although it was very obviously 

 present in the thirty-hour chick embryo. I find, however, that in 

 the ripe eggs and sperm of the sea-urchin Echinus miliai'is, it is 

 invariably present in very appreciable quantity, but one minute 

 after fertilisation the same eggs give a very pronounced magenta 

 coloiir by the nitro-prusside test. It is very readily washed out of 

 the eggs by heating them in sea- water in the presence of a little 

 acetic acid ; when its presence can be shown in the water, the. washed 

 eggs then no longer give the test. In the unripe- egg, in which the 

 egg nucleus is plainly visible, in a number of instances I could find 

 no trace of its presence. In the ripe eggs it is present in very 

 variable quantities, the eggs of no two females giving the same result, 

 probably depending on varying degrees of ripeness of their gonads. 

 In several samples of ripe sperm it was present in much greater 

 quantity than in any of the eggs examined. There are many 

 points of interest brought up by the presence of this remarkable 

 substance in the fertilised egg, and there is every reason to believe 

 its study in the future will reveal many interesting facts with regard 

 to the respiratory exchange in the egg on fertilisation. 2 



THE HEREDITARY EFFECTS OF FERTILISATION 



The attempts that have been made to interpret the nature and 

 essence of sexual reproduction may be ranged under two heads, 



1 Hopkins, "On an Autoxidisable Constituent of the Cell," Biochem. Jour., 

 vol. xv., 1921. 



2 Shearer, "On the Oxidation Processes of the Echinoderm Egg during 

 Fertilisation," Prw. Roy. Soc. Lond<m, B., vol. xciii., 1922. 



