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On the Oxidation Processes of the Echinoderm Egg during 



Fertilisation. 

 By C. Shearer, F.RS. 



(Eeceived November 15, 1921.) 

 I. Introduction. 



The following paper is concerned with an investigation of the oxidation 

 processes of the animal egg-cell during fertilisation. The subject has already- 

 received considerable attention and the problem has been approached from 

 many different aspects. The first to attempt to measure in definitive quantita- 

 tive manner the oxygen consumption of the egg on fertilisation, was Warburg (1) 

 in 1908. He made use of the sea-urchin Arbacia, and estimated the amount 

 of oxygen that had disappeared from the sea-water in which the eggs had 

 remained for some time. The Winkler titration method was employed. He 

 found that a quantity of eggs that gave a Kjeldahl determination of 28 mgrm. 

 of egg nitrogen, which corresponds roughly to about 4 million eggs, 4-5 c.c. of 

 oxygen was taken up in the first hour following fertilisation, while the same 

 quantity of unfertilised eggs only consumed - 5-0 - 7 c.mm. of oxygen in this 

 time. The fertilised egg, therefore, took up six to seven times more oxygen 

 than the unfertilised egg. Loeb had previously predicted, that the main 

 function of the sperm in the process of fertilisation was that of setting up a 

 series of oxidations on its entrance into the cytoplasm of the egg. Warburg's 

 work was a remarkable confirmation, therefore, of Loeb's prediction. This 

 first paper was followed up by a long series of papers which have added 

 greatly to our knowledge of the oxidation processes taking place in the egg on 

 fertilisation. In addition, our knowledge has also been greatly extended by the 

 numerous papers of Loeb, and especially the papers of Loeb and Wasteneys (2) 

 in which quantitative measurements were also carried out. In 1911 appeared 

 the large paper of Meyerhof (3) in which the heat liberation was measured 

 and correlated with the oxygen consumption. In all these papers the Winkler 

 method was employed ; there are, however, many drawbacks to the use of 

 this method, and in the recent work of Warburg and Meyerhof it has been 

 finally abandoned for the more convenient and accurate manometer. The great 

 advantage of the manometer method lies in the fact that it can be used equally 

 well for both oxygen and carbon dioxide determinations, and that continuous 

 observations can be carried out minute by minute on the respiratory exchange 

 of the material under investigation. Warburg (4) (1915), using this instrument, 

 has recently reinvestigated the respiratory exchange in the egg of the sea- 



