626 THE RESPIRATION AND [pt. iii 



with the respiratory rate, for they might be greatly depressed, and 

 even abohshed aUogether, without any effect on the respiration-rate 

 being perceptible. Thus, after 25 minutes in ordinary sea water, the 

 astropheres are visible, but nothing has happened at all in 1/2000 

 normal phenylurethane. After 40 minutes, the beginning of the 

 first cleavage is usually present, but in the phenylurethane eggs 

 the astropheres are only just appearing. After 90 minutes, the two 

 blastomeres are usually each beginning to divide, but the phenyl- 

 urethane eggs have only got as far as the equatorial plate stage. Yet 

 in spite of these profound differences, the oxygen consumption of the 

 two groups of eggs is not markedly different, the inhibition due to the 

 phenylurethane not being more than 20 per cent., as opposed to the 

 600 per cent, rise on fertilisation. Typical figures were 0-450 c.c. oxygen 

 per hour per 28 mgm. nitrogen for the normal ones and 0-438 c.c. 

 for the urethane ones. "The visible changes in the early developing 

 egg", as Warburg said, "are not conditions of the change in oxygen 

 utilisation after fertilisation. But on the other hand Loeb discovered 

 that oxygenation is a condition of the visible changes, so that those 

 chemical processes, the activity of which we can judge by the amount 

 of oxygen taken in, would seem to underly the morphological ones." 



The work of Runnstrom on echinoderm eggs is also very important. 

 He investigated the inhibition of respiration in mixtures of carbon 

 monoxide and oxygen, and found that it was always greater in the 

 case of fertilised or otherwise stimulated eggs than in the case of 

 unfertilised ones. With 96 per cent, carbon monoxide the inhibition 

 was on an average 64 per cent, if the egg was fertilised, but only 

 5 per cent, if the egg was unfertilised. He linked up these views in a 

 theoretical discussion with the colloidal changes known to take place 

 on fertilisation. In carbon monoxide atmospheres, membrane forma- 

 tion is unimpaired but no rise of respiratory rate takes place. As for 

 potassium cyanide, very much the same results were found as for carbon 

 monoxide, i.e. the inhibition was greatest on the fertilised eggs. 



Runnstrom concluded from these facts that the "Atmungsferment " 

 of Warburg (the indophenol oxidase system) is not "saturated", i.e. 

 not fully in contact with its substrates in the unfertilised eggs. Addition 

 of the Rohmann-Spitzer reagents makes the unfertilised eggs respire 

 just as fast as the fertilised ones, and the inhibition by CO is then the 

 same on both; therefore the "Atmungsferment" is just as active in the 

 former as in the latter. Again, methylene blue is reduced anaero- 



