344 THE UNFERTILISED EGG AS A [pt. iii 



monstrosa. Particularly interesting were his experiments with eggs — 

 he isolated considerable amounts of urea from a 5 cm. embryo of 

 Mustelus laevis, and from the yolk of Scyllium stellare and Myliobatis 

 aquila eggs, but he could find none in the surrounding jelly or "white ". 

 An Ggg ofPristis antiquorum yielded 3920 mgm. per cent, (wet weight) 

 and a Torpedo ocellata egg 1 740 mgm. per cent. An Acanthias vulgaris 

 embryo 1 7 cm. long had 3360 mgm. per cent, in its muscles, 1800 mgm. 

 per cent, in its liver, and 2640 mgm. per cent, in its unused yolk. 

 Other work on urea in selachians was done by Grehant and by 

 Rabuteau & Papillon. 



Table 42. Distribution of non-protein nitrogen in eggs. 



% of total non-protein N (including purine N) 



g-| z § iz g 2 -g I I |Z 



w.« „ „ ^ 2^ c S "G 2 o op Investigator 



Species HSo? cq <fe^ P U D U hUa and date 



Herring — 198 — 44-3 359 — — — — — Konig & Grossfeld (1913) 



Carp ... ... — 39-8 — 36-1 24-1 — — — — — >> >, 



Sturgeon ... — 25-2 13-6 55-4 189 — — — — — ,, ,, 



Herring ... ... 2060 244 67 21-6 — 519 None 18-3 — — Steudel & Osato (1923); 



Steudel & Takahashi (1923) 



Herring 1443 16-91 23-42 41-65 1802 — — — — — Yoshimura (1913) 



Silkworm ... 440 — 4-44 54-30 34-60 — - — — 610 6-7 Russo (1922) 



Hen (aver, figures) — 88-80 4-22 7-04 — None None Trace — — — 



Fresh- water gar 299 92-00 — 4-02 — — — 4-0 — — Nelson & Greene (1921) 



(not ripe) 



More light, however, was thrown on the reasons for this richness 

 in urea when in 1897 Bottazzi working on the osmotic pressure offish 

 blood, found that the elasmobranchs differed fundamentally from 

 teleosts in being isotonic with sea water. 



Serum 



A 



Selachians Torpedo marmorata —2-26° 



Trygon violacea —2-44° 



Teleosteans Charax pimtazzo —1-04° 



Serranus gigas — i -03° 



Bottazzi observed that the selachian osmotic pressure would corre- 

 spond to some 3-9 per cent, sodium chloride but laid no emphasis on 

 the fact that selachian blood did not contain anything like so much 

 ash. It was left for Rodier to show that the difference was made up 

 almost wholly by urea. Duval has since found that the salts alone 

 would only give an osmotic pressure of A — i-o6°. "High blood- 

 urea", as Smith says, "is a phyletic character of the orders Selachii 



