214 Dr. C. Shearer. On the Oxidation Processes of 



urchin Strongylocentrotus during the first 24 hours of development. He found 

 that a quantity of unfertilised eggs that contained 20 nigrm. of egg nitrogen, 

 which corresponds to about 3 million eggs, consumed in 20 minutes 

 10-14 c.mm. of oxygen at a temperature 23° C. and barometer 760 mm. Hg. 

 The fertilised egg under the same conditions, 10 minutes after the addition of 

 the sperm, consumed 60-84 c.mm. That is 10 minutes after fertilisation the 

 oxygen consumption of the egg was six times that of the unfertilised egg, and 

 that there was already a rise of 500 per cent, in the oxidation rate of the egg 

 in this time. In the sixth hour the oxygen consumption was twelve times 

 that of the unfertilised egg, at 12 hours it was sixteen times, while at 

 24 hours it was twenty-two times the amount of the unfertilised egg. As 

 "Warburg remarks, it is extraordinary that in one and the same cell substance, 

 which receives no addition of fresh material from any external source, we 

 should find, as the result of fertilisation in the course of 24 hours, a rise in its 

 oxidation rate of something like 2000 per cent. On the whole the mano- 

 meter method seemed to show that there was a much closer agreement 

 between the increase in the respiratory quotient and the appearance of visible 

 structure in the egg, than had been demonstrated in previous work where 

 the Winkler titration method had been employed. In all instances the C0 2 

 output of the eggs followed closely the oxygen uptake, the respiratory quotient 

 being in the neighbourhood of - 9. The respiration of a single spermatozoon 

 was found to be about 1500-2000 times less than that of the egg. 



In the past season, working at Naples, I have been able to carry the 

 investigation of the problem a step farther, by the use of a special type of the 

 Barcroft differential manometer, in which it was possible to bring about the 

 fertilisation of the eggs in the closed chamber of the apparatus, and so for the 

 first time the measurement of the respiratory exchange during the period the 

 sperm were actually making their way into the egg was rendered possible. 

 The eggs and sperm of Echinus microtubermlatus were used. 



II. Methods. 



In the previous experiments of Warburg (4) (1915), where the manometer has 

 also been employed, readings were only obtained 10 minutes after the addition 

 of the sperm. The following experiments will show that, by the end of this 

 time, the most important part of the process of the fertilisation of the egg has 

 already taken place. There is a great initial inrush of oxygen into the 

 egg and a corresponding output of CO2 within the first minute after the 

 addition of the sperm to the eggs. It is clear that the spermatozoon sets up 

 an instantaneous oxidation process in the egg, which is perhaps unparalleled 

 in reactions of the animal cell for its sudden character. 



