BIOCHEMISTRY OF THE SEXUAL ORGANS 317 



Loeb's work has proved of great heuristic value and has attracted 

 many workers to this fascinating field of cytochemistry. A very 

 interesting historical account of the whole subject together with a 

 very full bibliography is given by F. R. Lillie in his book, " Problems 

 of Fertilisation." l He criticises some of Loeb's conclusions and 

 contributes a new hypothesis. It is based mainly on the observation 

 that mature eggs of Arbacia and certain other invertebrates, when 

 suspended in sea-water, secrete a substance which agglutinates the 

 spermatozoa of the same species. It is a specific reaction and is 

 given only by mature eggs, and neither by fertilised eggs nor 

 by immature eggs. The jelly membrane of the eggs is saturated 

 with this substance, which Lillie calls " fertilisin." It has the 

 physical characters of a colloid, being nou-dialysable, and is very 

 heat resistant ; when allowed to act on spermatozoa it disappears 

 from the solution if not present in excess. It possesses a considerable 

 degree of specificity if tested against spermatozoa belonging to 

 different species. Its action on the spermatozoa is to agglutinate the 

 heads of the spermatozoa which swell, while the tails remain 

 unaffected. The adhesive property which the sperm develops under 

 these circumstances binds the egg to the sperm, and is evidence of 

 an intimate chemical combination of sperm- and egg-constituents 

 beginning at the very moment of union. The presence of the 

 agglutinating substance is necessary for the activation of development 

 in the egg of the sea-urchin, and Lillie suggests that as the result of 

 the interaction of this substance with the head of the spermatozoa a 

 substance is formed or released which activates the egg. " The 

 spermatozoon is conceived, by means of a substance which it bears 

 and which enters into union with the fertilisin of the egg, to release 

 the activity of this substance within the egg." 



Other workers look upon physical changes occurring in the 

 colloids of the ovum as the essential processes causing development. 

 Thus Yves Delage 2 looks upon the membrane formation which 

 precedes segmentation of the egg as a coagulation or gelation. This 

 is followed by disappearance of the nuclear membrane which he 

 interprets as a liquefaction or degelation. He therefore ^devised a 

 very successful method of artificial parthenogenesis in which the 

 application of a coagulative agent, namely tannic acid, is followed by 

 treatment with a liquefying agent, namely ammonia. 



Wolfgang Ostwald 3 has determined the amounts of oxidising 



1 Lillie (F.), Problems of Fertilisation, University of Chicago Press, 1919. 



Delage and Goldsmith, La Parthenogenese naturelle et experimental^ Paris, 

 E. Flammarion, 1913. 



3 Wolfgang Ostwald, " C T ber das Vorkommen von oxydativen Fermenten in 

 den reifen Geschlechtszellen von Amphibien und liber die Rolle dieser Fermente 

 bei den Vorgangen der Entwicklungserregung," Biochem. Zeitsch., vol. vi., 1907. 



