SECT. lo] THE NITROGENOUS EXTRACTIVES 1157 



he obtained i2-6 mgm. purine nitrogen from 2-96 gm. of dry substance, 

 or 0-425 mgm. per cent., and from those in the morula stage 1-721 gm. 

 gave him 7-56 mgm. nitrogen in the purine silver precipitate, or 

 0-439 mgm- per cent. In all cases 100 mgm. of total nitrogen con- 

 tained 4-6 mgm. of purine nitrogen. In just the same way there was 

 no change in the amount of nucleoprotein phosphorus up to the 

 morula stage (see p. 1245). Masing's results were afterwards criticised 

 by Robertson & Wasteneys on the ground that his material must have 

 contained excess of spermatozoa, which are, of course, very rich in 

 nucleoprotein, but this was not justifiable as Masing's unfertilised eggs 

 gave as much purine nitrogen as later stages. Subsequent work by 

 Needham & Needham on various invertebrate eggs strongly supported 

 Masing, for the nucleoprotein phosphorus was found to be constant 

 during development. 



Sand-dollar (Dendraster excentricus) 

 Starfish {Patiria miniata) 

 Sand-crab (Emerita analoga) 

 Brine-shrimp {Artemia salina) 



These facts are interesting in view of the great increase known to 

 take place in the total quantity of microscopically visible nuclear 

 matter during echinoderm development (see the figures of Godlevski 

 given on p. 11 5 1 ) . All the early workers believed that nuclein synthesis 

 occurred in echinoderm eggs, partly because, like Robertson, they 

 were convinced that the choline of lecithin was the causative agent in 

 cell-division, and the lecithin phosphorus must therefore be used in 

 other ways, and partly because, like Loeb, they were impressed by 

 the behaviour of the nucleoplasmatic ratio and identified nuclear 

 chromatin with the oxidations of the cell on the one hand and with 

 the supposedly autocatalytic character of growth on the other. The 

 flaw in these arguments was the identification of nuclear material as 

 seen through the microscope with nucleoprotein as measured 

 chemically. With regard to the marine invertebrate eggs so far studied 

 we must on the contrary picture an organisation of preformed nuclein 

 into the chromatin of the nuclei rather than a chemical synthesis of 

 it from other raw materials.^ 



1 An apparent contradiction exists here. The histochemical method of Feulgen and 

 Rossenbeck, which reveals the presence of nuclein, depends on a reaction of the aldehyde 

 group of the hexose constituent with fuchsin sulphonic acid. J. Brachet has shown that 



