SECT, i] PHYSICO-CHEMICAL SYSTEM 337 



quite similar results with the sea-urchin's egg, the egg of the silkworm 

 and the eggs of various Crustacea, echinoderms and an annelid. In 

 the sea-urchin egg purine bases were found accounting for 6 per cent, 

 of the total nitrogen as nucleoprotein nitrogen, while in the case of 

 Bombyx there were 20 mgm. per cent, dry weight. Again, Levene & 

 Mandel isolated from their ichthulic acid in 1907 0-344 P^^^ cent, of 

 guanine, 0-307 per cent, of adenine, 0-360 per cent, of uracil and 

 0-309 per cent, of thymine. Mandel & Levene were also able to 

 isolate nucleic acid from cod's eggs. It would certainly appear from 

 this evidence as if ichthulin and vitellin may be associated with small 

 quantities of nucleic acid. In this connection it is of interest that 

 Calvery has evidence that the chick embryo can synthesise "yeast-" 

 as well as animal nucleic acid. Steudel & Osato have also obtained 

 guanine and adenine from herring's eggs, but this was in the non- 

 protein nitrogen fraction, and there was therefore no evidence from 

 their work that any preformed nucleic acid was a constituent of the 

 egg. The most exhaustive investigation of the problem was that of 

 Konig & Grossfeld, who in 1913 set out definitely to clear up the 

 discrepancy. As perhaps might have been expected, they found that 

 they could isolate purine bases after hydrolysis from all the fish eggs 

 they studied, but only in small quantity; their results are shown in 

 Table 36. The question of nuclein synthesis by the developing 

 embryo will be discussed in relation to these findings in Section I0'3. 



Table 36. Investigations of Konig & Grossfeld. 



Total purine bases isolated 



Mgm.% 

 dry weight 



Herring 

 Carp 

 Cod ... 

 Pike ... 

 Sturgeon 



0-408 

 I -060 

 2-440 

 0-014 

 0-230 



But the exact relationship between the nuclein and the vitelHn 

 remains exceedingly obscure. It is possible that in one and the 

 same egg there may be more than one modification of vitelHn, 

 apart altogether from the insoluble form suggested by Steudel & 

 Osato. All the knowledge that we possess at the present time 



