424 



Dr. C. Shearer. Heat Production and Oxidation 



Summary. 



1. In the present paper an attempt has been made to measure the oxygen 

 consumption of the egg of Echinus miliaria on fertilisation and early develop- 

 ment and compare it with the amount of heat liberated by the egg at the 

 same time. 



2. In making both these estimations new methods have been employed. 



3. The oxygen consumption of the egg has been measured by the use of a 

 special pattern of the Barcrof t differential manometer, in which the eggs were 

 fertilised within the closed chambers of the apparatus. The C0 2 output of 

 the egg was also measured with the same instrument and the respiratory 

 quotient determined. 



4. The heat liberation was measured by the use of the differential micro - 

 calorimetric method. 



5. In 1 hour 1 million unfertilised eggs (8 mgrm. egg 1ST.) consumed 

 15 - 1 c.mm. of oxygen and gave off at the same time - 067 of a gram-calorie of 

 heat at standard pressure (760 mm. Hg.) and temperature 14 - 5° C. 



6. In the same time the same quantity of fertilised eggs consumed 

 86 - 4 e.mm. oxygen (with a corresponding output of C0 2 , respiratory 

 quotient 0'92) and liberated 0-3976 of a gram-calorie of heat under similar 

 conditions. 



7. The fertilised egg in the first hour of development gave off roughly 

 6 — 7 times more heat than the unfertilised egg and consumed at the same 

 time 6 or 7 times more oxygen than the unfertilised egg. 



8. In the fertilised egg in one experiment (I) 58 - 4 mgrm. egg nitrogen 

 (about 7 "3 million eggs) liberated 2 - 9 gram-calories at the end of the first 

 hour of development; in the fifth hour, 10'5 gram-calories and 22 - 8 gram- 

 calories of heat in 11 hours. In another experiment (II) 146 - 2 mgrm. egg 

 nitrogen (18 - 6 million eggs) liberated 6'35 gram-calories in the first hour, 

 28 gram-calories in the fifth hour, and in 11 hours 74 - 4 gram-calories. (This 

 last figure is possibly too high, due to some cytolysis.) On the whole the 

 heat liberation of the egg on fertilisation rises steadily, reaching its highest 

 point when segmentation has been completed and the free-swimming stage is 

 reached. 



9. The heat liberation of the egg during the first hour after the sperm 

 have been added to the eggs expressed in gram-calories divided by the 

 amount of oxygen consumed in the same time, expressed in milligrammes, 

 gives a calorific quotient (Q). 



10. In the case of the unfertilised egg the calorific quotient was found to be 

 about 3 - 07, while in the fertilised egg it was found to be 3"22. 



