FERTILISATION 223 



urchin eggs should segment if kept for a sufficiently long period, 

 and that it ought to be possible to induce segmentation by 

 appl5dng heat, since heat is known to accelerate chemical re- 

 actions, but neither of these results could be obtained. 



He then suggests the possibihty that the spermatozoon, in 

 conjugating with the ovum, removes from the latter a negative 

 catalyser or condition whose existence in the ovum somehow 

 inhibits the process of development. This suggestion seems to 

 provide an explanation of the secretory phenomena, which, on 

 Loeb's hypothesis, are the cause of the membrane formation. 

 " Finally, we may be able to understand a fact which [has been] 

 observed in the eggs of a starfish, and which has not yet been 

 mentioned, when the eggs of Asterina or Asterias are allowed to 

 ripen, they wiU die within a few hours unless they develop 

 either spontaneously or through the influence of sperms or 

 some of the above-mentioned agencies. The disintegration 

 which leads to the death of the non-developing egg is obviously 

 due to an oxidation, since I found that the same eggs when 

 kept in the absence of oxygen will not disintegrate. We know 

 that oxygen is an absolute prerequisite for the development 

 of the fertihsed egg " [but this statement is disputed by Delage]. 

 The fact that oxygen is a poison for the mature but non- 

 developing egg shows that the chemical processes which occur 

 in the unfertilised, non-developing egg must be altogether 

 different from those which go on in the developing egg of the 

 star-fish.^ 



' Loeb, loc. cit. See also " The Toxicity of Atmospheric Oxygen for the 

 Eggs of the Sea-Urchin after the Process of Membrane Formation " ; "On 

 the Necessity of the Presence of Free Oxygen in the Hypertonic Sea-water 

 for the Production of Artificial Parthenogenesis" ; " On the Counteraction of 

 the Toxic Effect of Hypertonic Solutions upon the Fertilised and Unfertilised 

 Egg of the Sea-Urchin by lack of Oxygen," Univ. of California Publications : 

 Physiology, vol. iii., 1906. See also " Versuche ilber den Chemischen 

 Charakter des Befruchtungsvorgangs," Biochem. Zeiischr., vol. i., 1906. 

 " Weitere Beobachtungen iiber den Einfluss der Befruchtung und der Zahl 

 der Zellkerne auf die Saurebildung im Ei," Biochem. Zeiischr., vol. ii. 1906 ; 

 "tjber die Superposition von kiinstlichen Parthenogenese und Samenbefruch- 

 tung in derselber Ei," Arc\. f. Entwick.-Mechanik, vol. xxiii., 1907 ; " Uber 

 die allgemeinen Methoden der kiinstlichen Parthenogenese," Pfliijer'e Arch. , 

 vol. cxviii., 1907 ; and other papers in the same volume. The following 

 papers also deal with artificial parthenogenesis in various animals : Delage, 

 0. R. de I'Acad. des Sciences, vol. cxxxv., 1902 (describing fertilisation by' 



