68 FERTILIZATION 



though Lindahl (1938) does not think this Hkely; alternatively, 

 their respiration may be stimulated by CO, which is known to 

 occur in other tissues (Daly, 1954). A further complicating factor 

 in CO-inhibition studies is that the respiration of unfertilized sea- 

 urchin eggs is depressed in the presence of strong light, which 

 must be used to obtain photo-reversal of CO-inhibition. 



In the light of what has been said above, I am inclined to think 

 that, for historical reasons, Needham placed too much emphasis 

 in Biochemistry and Morphogenesis on the alleged change-over at 

 fertilization from a non-ferrous to a ferrous type of respiration. 

 In other respects his section on Respiration, pp. 562-605, is ex- 

 cellent and contains a good deal of information omitted, for reasons 

 of space, from this chapter. 



To sum up, changes in Oo uptake at fertilization depend on the 

 time after shedding or removal from the ovary when fertilization 

 occurs; on the state of maturation of the egg at fertilization; and 

 on the previous history of the animals from which the eggs were 

 obtained. These factors may result in there being an increase, no 

 increase, or a fall in respiration at fertilization. The transient in- 

 crease in O2 uptake, which occurs immediately after fertilization, 

 has only been observed in sea-urchin eggs (apart from an early 

 experiment, which should be repeated, on Funduliis eggs) ; the same 

 applies to acid production and the low R.Q. at this time. The lack 

 of systematic examination of other eggs, particularly in regard to 

 acid production, is a serious lacuna in our knowledge. The cyto- 

 chrome system is present and functioning in unfertilized and ferti- 

 lized eggs. No qualitative changes in the behaviour of this system 

 occur at fertilization. 



