DK. W. H. BANSOM ON THE OVUM OE OSSEOUS EISHES. 
471 
degrees of opalescence were seen in most of the eggs. Examined by a power of X 35, 
the opaque ova had their inner sacs ruptured and shrunken in degrees, varying with the 
opacity, the discus germinativus being lobular and darkly granular. Those ova which 
were faintly opalescent only, exhibited but slight shrinking of the inner sac, which had 
evidently healed soon after rupture ; the site of this was marked by a deep pit sur- 
rounded by radial folds. Gradually, under the influence of the warmth of the room, the 
slight contractions natural to this stage returned. Zero-galvanic currents produced 
strongly marked contractions in these eggs. Those which were only thus partially 
ruptured, cleft for the first time about five hours after impregnation, but the masses 
were not symmetrically arranged, so that perhaps in this way also monsters may be 
formed (Plate XVIII. fig. 71). 
Cold, then, delays the changes which follow impregnation, but does not, within those 
limits which fall short of mechanical rupture and complete derangement of the structure 
of the egg, destroy irritability. Observations are wanted, however, with eggs cooled 
down to the state described in experiment b, upon an insulated stage, kept at the 
required temperature, while the galvanic current is applied. 
Observations were then made on the effects of elevated temperatures, upon the move- 
ments of the yelk, and on the cleavage. 
Control experiment. — Ova impregnated and kept at the temperature of the room 
(58° F.), were 30 m after, contracting and rotating slightly, 45 m after, vigorously, 2 U 30 ra 
after, were not cleft, but 6 h 30 m after, were cleft into eight masses. 
Experiment d . — Ova ten minutes after impregnation, being warmed on the stage of the 
microscope to about 73° F., at first did not seem to be influenced ; but after ten minutes’ 
continuance of the warmth, they were seen to be moving more rapidly than those of the 
control experiment. The temperature was then raised to about 80° F., which, after 
some minutes, produced a state of almost complete rest, with the yelk-ball globular, the 
discus germinativus nipple-shaded, and the oil-drops displaced. At the same time the 
control ova were vigorously contracting. Being then removed, and left at the tempera- 
ture of the room, they completed the first cleft at l h 50 m after impregnation, and by 
6 h 30 m after, were cleft into the coarse mulberry stage, and much in advance of the 
control ova ; a fact, the more remarkable, because the contractions had been arrested 
for a time by the highest temperature used. In this experiment' the thermometer was 
laid upon the cell, but probably indicated a temperature somewhat higher than that 
reached by the eggs. 
Experiment e . — Ova ten minutes after impregnation, put into a chamber, warmed to 
83° F., and kept there for twenty minutes, were found actively contracting. In this case 
I had reason to think that they did not reach the temperature of the chamber, which 
was then heated to 102° F., and after some minutes, when the control ova were actively 
contracting, these eggs became relaxed and still, so that their globular yelk-balls filled 
the yelk-sac, and effaced the breathing-chamber, and the oil-drops were displaced and 
scattered. On cooling the eggs again slowly to 58° F., the contractions reappeared in 
mdccclxvii. 3 s 
