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 amino- 



acids, glutamic acid and cystine, to which Hopkins 1 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 the 



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 miliaris, it is 



invariably present in very appreciable quantity, but one minute 



after fertilisation the same eggs give a very pronounced magenta 



colour 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," Biockem. Jour., 

 vol. xv., 1921. 



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

 Fertilisation," Proc. Roy. Soc. London, B., vol. xciii., 1922. 



