148 Part III. — Sixteenth Annual Report 



The AurouNTs of Sodium Chloride in the Vitelline Fluid op the 

 Unripe and Eipb Plaice Ova. 



The common salt was selected for analysis, because it is the salt 

 present in largest amount, and is also the most diffusible one. In addi- 

 tion, it is the probable causal agent at play in the clearing up of the 

 yolk in the final stage of maturation : — 



I. Immature Plaice Ova. — 52-531 grammes fresh unripe ova 

 (=-18-187 grammes water-free ova) were broken down in a mortar, and 

 extracted with 500cc. distilled water, filtered, and filtrate boiled, and then 

 precipitated with alcohol. In the filtrate the chlorides were estimated by 

 Mohr's method, and were found to amount to '214 grammes NaCl., or 

 in each ovum '0031 milligramme NaCl. 



II. Mature Plaice Ova. — 16*007 grammes were treated in the same 

 way as the unripe ova. They were found to contain "0945 gramme NaCL, 

 or in each ovum '020 milligramme NaCl. That is to say, during 

 maturation there is a marked increase in the chlorides accompanying the 

 increase in water. 



Substances which Diffuse Out into Distilled Water from 

 Unripe and Ripe Plaice Ova. 



In order to find out the form in which the albumins, salts, etc., are 

 bound in the ova, I took weighed quantities of ripe and unripe eggs, and 

 allowed them to circulate through distilled water for fixed periods. All 

 the chloride present as inorganic salt in the vitelline fluid passed out into 

 the water, and, in addition, a small extra amount of chlorides passed out 

 beyond that which had been present as sodium chloride in the yolk. 

 This extra amount of chloride had evidently been bound with albumin, 

 and the combination was broken up during the process of diffusion. 

 This points to the active part which the chlorides must play in the clear- 

 ing up of the yolk. This holds for both the ripe and unripe eggs. 



Of the total phosphorus in the unripe ova before diffusion, 10*47 

 per cent, diffuses out, and all of this practically is in organic combination, 

 and is precipitable with alcohol. That is to say, the organic phosphorus- 

 holding constituent of the yolk of the plaice ovum is an easily diffusible 

 body. This is a point of great importance, for, as we shall see, there is a 

 similar body in the ovarian fluid. 



Of the total phosphorus present in the ripe plaice ovum, 52*6 per 

 cent, diffuses out during the same time, and under the same conditions, 

 as in the case of the uuripe ova. Practically all this phosphorus also is 

 in organic form (vitellin). The organic form of the body is maintained 

 after diffusion into the distilled water. 



Of the total albumin in the unripe ovum, 1*414 per cent, diffuses 

 out; and of the total solids diffused, 8 '78 per cent, is in the form of 

 albumin. In the ripe ovum, on the other hand, 3-294 per cent, of the 

 total albumin passes out, but of the total solids diffused, only 6*145 per 

 cent, is in the form of albumin. 



That is to say, everything points to the fact that in the ripe ovum 

 the substances present are in a condition more suitable for diffusion than 

 in the unripe. Some of the important points with regard to the phos- 

 phorus I have already emphasised ; but there is still one of great import- 

 ance that I have just referred to, and that is the amount of inorganically 

 and organically bound phosphorus in the unripe and ripe ova. 



