342 



THE UNFERTILISED EGG AS A [pt. iii 



Table 41. Distribution of 



* With so % mucoprotein and 



Within the non-protein nitrogen fraction itself there are some 

 fragmentary data for the distribution, as may be seen from Table 42 . 

 Unidentified compounds usually account for from 20 to 35 per cent, 

 of the total non-protein nitrogen, and free amino-acids for approxi- 

 mately half of it. Among those identified by Steudel & Osato were 

 histidine, arginine, lysine and cystine. The ammonia may vary from 

 4 to 25 per cent., and the purine bases from 15 to 40 per cent. 

 As far as can be seen at present, the hen's egg seems to possess 

 the greater part of its non-protein nitrogen in the basic fraction. 

 The most interesting point brought out by the table is probably the 

 significant quantity of urea shown to be present by the analyses of 

 Steudel & Osato, amounting to no less than half of the total non- 

 protein nitrogen, and it is possible that a good deal of the unidentified 

 nitrogen of Konig & Grossfeld might be accounted for in this way. 

 The presence of nitrogenous excretory products in the undeveloped 

 egg, though at first sight paradoxical, is nevertheless undoubtedly a 

 fact in the case of some aquatic organisms. The hen's egg contains 

 hardly a trace of urea at the beginning of development but that of 

 a selachian fish contains a good deal (see Section 9- 1 1 ) . 



