BIOCHEMISTRY OF THE SEXUAL ORGANS 301 



of these ferments: — especially the peroxidase — ^is increased when 

 the extracts of ova are mixed with the extracts of spermatozoa. 



The development of the ovum after fertihsation is, according 

 to Ostwald, due to this activation of the oxidising ferments 

 inducing a chemical synthesis of nuclein substances, which form 

 a locahsed coagulum of a definite orientation, namely, the 

 astrosphere. According to the view of Fischer and Ostwald,^ 

 which is, however, not accepted by other workers,^ the forma- 

 tion of the astrosphere initiates cell-division, and therefore the 

 development of the egg. 



A very ingenious theory of the chemical mechanism of ferti- 

 lisation has been put forward recently by Loeb,^ as the result of 

 his work on artificial parthenogenesis. According to Loeb, the 

 development of the mature ovum is dependent upon two processes. 

 It is initiated by a cytolysis affecting the periphery of the cell. 

 This process, which is accompanied by the formation of a ferti- 

 lisation membrane, can be induced by any agent having a cyto- 

 lytic action, such as heat, ether, fatty acids, saponin, or the serum 

 of an animal of a different species. If this initial cytolysis is 

 allowed to proceed unchecked, the eggs, although they may 

 begin to divide, eventually undergo complete cytolysis. If, on 

 the other hand, the initial cytolysis is inhibited by suitable means, 

 such as treatment with potassium cyanide or immersion in 

 hypertonic sea-water containing oxygen, the eggs will develop in 

 the same way as if they had been fertilised by a spermatozoon. 



If it be admitted that artificial parthenogenesis represents the 

 conditions governing fertihsation by a spermatozoon, then it 

 follows that a spermatozoon should contain two substances, 

 namely, a cytolysin, and a substance inhibiting the initial cyto- 

 lysis. The presence in the spermatozoon of a cytolysin can indeed 

 be proved. Extracts of the testis of a cock, or the dead semen 

 (killed by heating) of a starfish or a mollusc, will induce the 

 initial process of cytolysis in the eggs of a sea-urchin. The dead 

 semen of a sea-urchin, however, is quite inactive against the eggs 

 of a sea-urchin. This is in agreement with our knowledge of 



' Fischer and Ostwald, " Zur Physikalisch-Chemischen Theorie der 

 Befruchtnng, " Pfiiigtr's Archiv, vol. cvi., 1905. 



^ See, for instance, Burrian, loc. cit. 



' Jacques Loeb, Die chemische Entwicklungserregung des tieriachen 

 Eies, Berlin, 1909. 



