86 FERTILIZATION 



COCH, 



HO. 

 Usnic acid, T f 1 ^^ believed to inhibit 



H3C y CH3 I COCH, 



OH OH 



DN-ase when cobalt is present, though it is also thought to interfere 

 with oxidative phosphorylation. As several workers have put forward 

 the view that the biological activity of unsaturated carbonyl com- 

 pounds is due to their additive interaction with thiol compounds 

 (Sexton, 1949), the effects of cysteine and thioglycollic acid on usnic 

 acid inhibition would be of interest. The fusion of the pronuclei is 

 also inhibited by anaerobiosis and HCN (Runnstrom, 1935a). 



(10) Increase in alkaline phosphatase after f. P. lividiis (Wick- 

 lund, 1948). 



(10. 1 ) No change in alkaline phosphatase until 10 hours after f. 

 P. miliaris (Gustafson & Hasselberg, 1950). 



(10-2) No change in acid or alkaline phosphatase until gastrula- 

 tion. A. punctulata (Mazia et al., 1948*). 



(10.3) No sudden change in alkaline phosphatase after f. X. 

 laevis, S. mexicanum (Krugelis, 1950). 



(11) Transient NH3 production at f. P. lividtis (Orstrom, 

 1941). 



(ii.i) Non-transient NH3 production after f. A. punctulata 

 (Hutchens et al., 1942). 



This work has been criticised on technical grounds by Lindberg 

 (1945)- 



(11.2) f. eggs form glutamine from added NH3 and glutamic 

 acid, u, eggs do not. P. lividns (Orstrom, 1941). 



(12) No change in 'free' hypoxanthine and guanine, present in 

 the ratio 2:1. R. temporaria (Steincrt, 1952). 



(13) No change in free 'cholesterol' at f. E. cordatum (Ohman, 

 1945)- 



