444 
DR. W. H. RANSOM ON THE OVUM OE OSSEOUS FISHES. 
small eggs ; and if the fragment has been prepared in an abundance of water at first, 
the free vesicles may show no molecular deposit in the colloid matrix after seven hours 
(Plate XV. fig. 18). 
The germinal spots, after this prolonged action of water on the free vesicles, are not 
soluble in a 10 per cent, solution of acetate of potash, but the spots in the unbroken 
larger ova are ; thus water must chemically change the substance of the spots or their 
surface, as before its action 2^ per cent, of the same salt dissolved them. 
A 1 per cent, solution of glycerine is an excellent medium for showing the germinal 
spots ; they remain for ten minutes in it without showing changes of form or vacuola- 
tion even in the free vesicles. It does not precipitate the colloid matrix. 
A 1^ per cent, solution of chloride of sodium, which does not change blood-corpuscles, 
added to a fragment of ovary, prepared in the maternal fluids, made the colloid matrix 
which was not previously granular look brighter, and changed the germinal spots from 
round homogeneous-looking bodies to variously tailed and vacuolated forms (Plate XV. 
fig. 19). On then gradually increasing the strength of the solution to 5 per cent., it was 
observed in a ruptured free vesicle that the germinal spots, as they lay adhering to the 
colloid matrix near, and partly within the rupture, gradually became paler, coalesced, and 
fused into a large pale drop, with vacuolation in and around it. The stages of this 
change are seen in Plate XVI. fig. 20. Precisely similar changes were seen to occur in 
the spots of germinal vesicles while yet contained in the eggs. It seems probable, then, 
that we must look on the germinal spots as drops of a thick fluid, or at least not as solid 
bodies. 
A solution of only 2^ per cent, of chloride of sodium which crenates the blood-disks, 
similarly caused fusion of the germinal spots. In a solution of 1 per cent, only, the spots 
vacuolate and become tailed very slowly, and after an hour I found them again round — 
suggesting the possibility that they may have a power of changing their form analogous 
to that possessed by the protoplasm of white blood-corpuscles. This solution causes 
the red blood-disks of the same fish to become paler : it does not ultimately dissolve 
the spots, but like water changes them, so that they are no longer soluble in even a 10 
per cent, solution of chloride of sodium. 
The solutions of acetate of potash act very much like those of chloride of sodium. 
A weak acetic acid solution does not dissolve the wall of the germinal vesicle or 
further distend it. It precipitates the colloid matrix, leaving the spots dark-bordered 
and distinct. 
The yelk-sac also merits a minute investigation. 
The precise period at which it is formed is difficult or impossible to determine. In 
the smallest eggs seen, those of -g^o”? if is n °f separable, but is probably indicated by 
the smooth hard outline which the yelk shows on its surface, when a2| per cent, solution 
of glycerine or of chloride of sodium is used, which contracts the yelk-ball with the 
yelk-sac, and leaves a space between it and the ovisac. A little later it is seen indicated 
by folds on the surface of the yelk, the result of the shrivelling which the solution 
