i88 THE PHYSIOLOGY OF REPRODUCTION 



also have evidence against the view that the nucleus plays the 

 predominant part in the oxidation processes of the cell. 



Tt would appear from Masing's 1 work that there is no actual 

 synthesis of nucleic acid in the egg-cell during early development. 

 He found as much nucleic acid in the fertilised unsegraented egg as 

 in the 8-cell stage. In the 8-cell stage we have eight nuclei almost 

 the size of the nucleus of the fertilised unsegmented egg. To 

 account for these facts Masing suggests that in the unsegmented 

 egg, only a part of the nucleic acid is contained within the nucleus, 

 most of it being distributed throughout the cytoplasm, but as 

 segmentation progresses this cytoplasmic portion is gradually with- 

 drawn within the new nuclei. 



In addition to Warburg's work, Meyerhof '- has also carried out 

 a series of extensive researches on the energy changes taking pface 

 within the egg of the sea-urchin Strong/ ocentrotits during fertilisation 

 and early development. The* heat production of the egg was 

 measured and correlated with the amount of oxygen consumed. 

 The heat liberated by the eggs was determined by means of a finely 

 divided Beckmann thermometer, the eggs being contained within 

 a small vacuum flask, sunk in the water of a carefully regulated 

 thermostat tank. The oxygen consumption was estimated by the 

 Winkler method. 



Meyerhof found the heat production of a quantity of unfertilised 

 eggs, containing 140 ing. of nitrogen (about 17 million eggs), to be 

 about 0*9 gram-calorie per hour, while the same quantity of fertilised 

 eggs liberated 4-4'2 gram-calories in this time. In the second hour, 

 the 2-cell stage, the heat production rose to 4'5-5 gram -calories. 

 In the fourth hour, corresponding to the 8-cell stage, it was 

 6-6'."> gram-calories. In the sixth hour, the 32-cell stage, it was 

 9'8 gram-calories, and from this stage onwards the heat liberation 

 increased rapidly, until in the eighteenth hour, when the free 

 swimming stage was reached, it was IT'S gram-calories per hour, 

 or four times the amount in the first hour following fertilisation. 



The heat given off by a known quantity of eggs, expressed in 

 gram-calories per hour, divided by the quantity of oxygen consumed 

 in the same time, expressed in milligrams, gave Meyerhof a calorific 

 quotient. He found this quotient for the early stages of develop- 

 ment to average 2'75, but if the heat of solution of carbon dioxide 

 and its combination to form sodium bicarbonate in sea-water is 

 taken into consideration, this value is reduced to 2'6. This figure 

 i- ii'inarkably low, for Ziinst and Schumburir, Ranber, Pfliiger and 



1 Masing, "Ubet 1 das Verhalten der Nucleinsiimv l>ci <lrr Furduing des 

 Seeigeleis," 'Z<-it*>-l>. f. /V V /.W. ('!,<<., v..l. Ixvii., 1910. 



2 Meyerhof, " Untersuchungen iiber die Warnietonung der vitalen 

 Oxydationsvorgange in Eiern," I., II., III., Biocftem. Zeit., vol. xxxv., 1911. 



