of the Fishery Board for Scotland. 



141 



Lecithin. — The alcohol and ether extract containing the lecithin was 

 evaporated to dryness by distilling off the alcohol and ether, and the 

 phosphorus of the residue was estimated. Amount of phosphorus 

 X 7 "2703 = lecithin (stearic acid form). 



The residue was tested for cholin and for the fatty acids. 



As the clearing up of the egg contents might not simply be due to the 

 endosmosis of water, but of neutral salts such as NaCl., or acid salts such 

 as Na PO4, the amount of NaCl. present was estimated in the ash of 

 the ova by Mohr's method — that is to say, the chlorides were estimated 

 with a AgNOg solution, each CC of which was equal to lOmgm. of 

 NaCl. 



The acidity was estimated by extracting the pounded ova with water 

 (dist.), squeezing out the fluid after filtering through muslin, and then 

 titrating with one-fifth normal NaOH. 



In some cases (and this will be repeated later) the ovarian fluid was 

 examined carefully, especially for NaCl., albumin, acid salts, in addition 

 to the specific gravity being taken. 



The same methods were employed as have been described in the 

 preceding pages. 



CHANGES IN PELAGIC AND DEMEESAL OVA OF MARINE 

 TELEOSTEANS DURING MATURATION. 



I. — Change in Volume. — A. In Pelagic. 



Dr. Fulton, in a thesis presented for M.D. degree in Edinburgli 

 University, gave a list of the volume of the ova of different fishes in the 

 immature and mature conditions. They were based upon the calculation 

 of the volume from the diameter of the ova, presuming that the latter were 

 complete spheres. To avoid as far as possible the fallacy of individual 

 differences in form, Dr. Fulton based his calculations upon the average 

 diameter of thirty or more ova. I have calculated the volume of a number 

 of the same ova and of some other varieties. The increase in volume of 

 the better-known marine Teleosteans, from the opaque immature to the 

 transparent or translucent mature ova, varies from about 1 : 3 to 1 : 5. 



The most marked increase in the volume of the ovum during ripening 

 occurs in the egg of the plaice, where the ripe egg is fully five times 

 larger than the unripe. In fact, in some that I have examined the ripe 

 was six times larger than the unripe. 



B. Demersal. 



This increase in volume is common also to the demersal eggs, the most 

 important variety being the herring. I give here the result of a number 

 of measurements of these ova : — 



Volume. 



Unripe, 1-022 cub mm. — 1-0226 



Ripe, 2-132 „ 



Here the increase in volume is much less than in any of the pelagic ova. 

 In Cottus scorpius the ripe eggs have a volume of 4*188 cub. mm.; the 

 unripe eggs I have not examined. 



In Cyclopterus lumpus (Lumpsucker) the ripe eggs have a volume 

 practically the same as those of Cottus scorpius, viz., 4*18 cub. mm. 

 Here also I have not examined the unripe ova. 



