E. HOFF-J0RGENSEN 



during the first day, but picks it up actively on the second day, by which time the 

 synthesis of nucleoprotein is presumably going on. 



E. Zeuthen. I should like to call attention to a paper by Blanchard (1935, J. biol. 

 Chem. 108, 251) who isolated 1 08 g. deoxynucleic acid from 4,820 g. of (wet) 

 Arbacia eggs. The substance yielded negative biuret reaction, negative tests for 

 pentose, and a positive Feulgen reaction. It contained 16 35 per cent. N and 10-13 

 per cent. P. Upon hydrolysis with 5 per cent. H 2 S0 4 it yielded 1 1 4 per cent, guanine 

 and 9 87 per cent, adenine, all values close to what is reported for DNA from other 

 sources. RNA was demonstrated in amounts about equal to DNA. 



Hoff-Jorgensen (for unfertilized Arbacia lixula eggs) finds 0*65 per mil. of the dry 

 matter to be DNA. This would seem to compare reasonably well with Blanchard's 

 value o 23 per mil. for wet Arbacia punctulata eggs. The important fact remains that 

 already in 1935 DNA seems to have been isolated from unfertilized sea-urchin eggs 

 in yields which we can now see indicate that the egg holds far more DNA than the 

 spermatozoon. 



The excess DNA of the egg may be either in the nucleus or in the cytoplasm. With 

 special regard to the sea-urchin egg I have (Pubbl. Staz. zool. Napoli 23, suppl. 1951) 

 suggested the latter possibility as the only one that would bring into harmony the 

 very different results obtained for the whole egg and (cf. Lison and Pasteels, 1951, 

 Arch. Biol. 62, 1 ) for the nucleus alone. 



A recent finding by Agrell (1953, Ark. <W.) that the basophilia of the cytoplasm 

 decreases in early cleavage can be taken as further support of the idea that nucleic 

 acids move from the cytoplasm to the new nuclei as they form. I do think, therefore, 

 that several lines of evidence available for the sea-urchin egg support the conclusion 

 derived with Hoff-Jorgensen's method, that the cytoplasm of mature eggs stores 

 DNA in amounts which — roughly — are in proportion to the egg size. 



90 



