484 
DR. W. H. RANSOM ON THE OVUM OE OSSEOUS EISHES. 
part of ova to sixteen of water without covering the surface with oil. After twenty 
hours the rhythmic contractions of the yelk were vigorous, the formative yelk was 
lobular, and often detached in part or wholly. After fifty-three hours they were con- 
tracting freely, several inner sacs ruptured. After seventy-two hours most of the inner 
sacs were burst, and the yelks were more or less opake, and no contractions were seen 
in those few in which the inner sac was not ruptured. The water was slightly opalescent. 
100 hours after, the water did not precipitate baryta-water, the broken eggs reddened 
blue litmus. Several of these eggs, from the deeper layers in the vessel, had not pro- 
perly imbibed water ; indeed the very lowest, fifty-three hours after, had the appearance 
of eggs freshly expressed from the fish, being still adhesive ; they could not then be 
made to absorb water freely as fresh eggs do. 
Control experiment 1'. — I fecundated ova successfully in ordinary distilled water, not 
covered with oil, by dropping in a fragment of ripe testis. Many of them cleft, but the 
water soon became turbid; and fifty-three hours after, many of them had opaque germinal 
masses ; seventy-two hours after, all were opaque, decomposition being evidently favoured 
by the presence of the fragment of testis. 
Control experiment 2. — I fertilized some spawn in the usual way in tap-water contained 
in a dish, and changed the water daily. Not all of these ova were impregnated, but the 
fecundated and n on-fecundated were seen rhythmically contracting with equal vigour 
twenty-five hours after, when the former were in the mulberry stage of cleavage. At 
fifty-seven hours, at seventy-five hours, and 100 hours after, the same contractions were 
seen in all the unimpregnated eggs, of which the inner sac yet contained some yelk, 
and in the impregnated ones in that part of the food-yelk still uncovered by the 
advancing germinal mass. The unimpregnated ova were all still the next day. The 
fertile eggs were hatched from the 16th to the 18th of April, that is, after eleven to 
thirteen days. 
Experiment a . — The fish being secured on a raised shelf, and the beakers on supports 
near, I passed the tube filled with oil into the sexual aperture, and held it in position 
by means of the elastic threads. Then by gentle pressure upon the abdomen the ova 
were made to pass into the tube until they had displaced the oil, the lower end being 
closed by a drop of oil. Unimpregnated ova were then passed through the tube, 
into one of the beakers, in the proportion of about one part of ova to ten of water, 
so that the tube dipping below the layer of oil, the eggs were scarcely, if at all, greased. 
After twenty-seven hours their yelks were contracting and oscillating freely ; the discus 
proligerus was concentrated and had become irregularly lobular, and often detached in 
fragments, or as a whole ; the detached masses being granular and opaque. The food-yelk 
was clear. The upper layers of the eggs in the beaker, however, alone exhibited these 
movements distinctly, the lower ones not having imbibed enough water to duly distend 
them ; hence they were not clear on the general surface, and had not a well-concentrated 
discus proligerus. At this time the contractions of the eggs in the upper layer were as 
strong as in control experiment 1. After forty-nine hours the lower layers of the eggs, 
