336 THE UNFERTILISED EGG AS A [pt. iii 



to a revivification in a subtler form of the old biogen molecule 

 theory (though it is to be hoped that it will not), not only as regards 

 the egg-cell but as regards protoplasm in general, we shall at any 

 rate possess in the spectrophotometer a powerful means of studying 

 the untouched normal cell-interior. 



Doubt exists with respect to the presence of reducing carbohydrate 

 in the ichthulin molecule. Levene & Mandel obtained minimal 

 quantities of laevulinic acid from their cod ichthulin, but this 

 finding was associated with the presence of purine bases. Six years 

 earlier Levene had been unable to find a trace of glucosamine in 

 cod ichthulin. Similar negative results were obtained by Steudel & 

 Takahashi on herring, and by Hammarsten on perch, ichthulin. 

 But the presence of glucosamine in notable amounts has been 

 reported for Torpedo ichthulin by Rothera, and for carp ichthulin by 

 Walther. While it is possible, and even probable, that ichthulins 

 from different fish eggs may vary much, it would be very desirable 

 to know to what extent this is the case, and a comparative study 

 of ichthulins is much needed. As we have seen Levene & Mori have 

 isolated a trisaccharide from avian vitellin. 



Closely allied to the question of the presence of carbohydrate 

 groupings in the ichthulin molecule is the equally disputed problem 

 of the presence of purine bases in the undeveloped tgg. We have 

 already seen that Miescher's identification of nucleoprotein with 

 vitellin was quite erroneous, and have described how he was set 

 right by Kossel. For the hen's &gg, it is now fairly clear that nucleins 

 are present only in exceedingly small amounts at the beginning of 

 development, not exceeding, for instance, i or 2 per cent, of the total 

 nitrogen or phosphorus. But there has been more difficulty in de- 

 ciding what is the real state of affairs in the eggs of fishes and 

 aquatic invertebrates. Walther (carp), Hugounenq (herring), Linnert 

 (sturgeon), and Hammarsten (perch), all examined the ichthulin of 

 these eggs for nucleic acid, and all failed to find the least trace of it. 

 Henze, on the other hand, working with the whole tgg of the 

 cephalopod. Sepia officinalis, isolated considerable amounts of purines 

 together with no less than 1-15 gm. per cent, of a pentose. Tscher- 

 norutzki a little later found that 10 per cent, of the total phosphorus 

 of the herring's egg could be accounted for as nucleoprotein phos- 

 phorus, and the nucleoprotein itself amounted to i-ig gm. per cent, 

 dry weight. Masing; Tichomirov, and Needham & Needham reported 



