482 
DR. W. H. RANSOM ON THE OVUM OF OSSEOUS FISHES. 
escapes into this solution, they go on, provided the inner sac is not too much injured. 
A 2 per cent, solution is too strong, it causes prompt rupture of the inner sac, but does 
not dissolve it. 
Ether . — Unimpregnated ova, thirty hours after deposition, while freely contracting, 
put into a watch glass, with only enough water to moisten them, and exposed to the 
vapour of ether under a small bell-glass, exhibited no diminution of movements, 
although slight opacity of the eggs was produced. Similar eggs treated with an aqueous 
solution of ether, became opaque, and exactly in the same ratio the movements became 
slower, and ultimately ceased. The opacity preceded any visible diminution of the 
movement. 
Chloroform . — Some chloroform in vapour was applied 144 hours after impregnation, 
at which time the heart is seen beating, the muscles of the trunk acting, and the yelk 
still contracting at the lateral abdominal poles. The first effect was to excite writhing 
movements in all the embryos, but in five minutes the muscles of the trunk and the 
heart had ceased to move, and the contractions of the yelk were arrested, the sulcus 
remaining uneffaced. Five minutes later the embryos began to recover, the yelk-con- 
tractions moved on slowly, and after adding fresh water the heart began to beat feebly ; 
but the trunk could not be seen to move in any of the embryos for half an hour in spite 
of free addition of water. After hours the trunk moved freely, the heart beat regu- 
larly, and the yelk contracted vigorously. 
As the general result of these observations, and those of a similar kind made on the 
ova of the Gasterosteus, it may be stated that the rhythmic contractility of the yelk is 
not materially influenced by any of the poisons used, which did not act chemically, with 
the exception of chloroform and of carbonic acid, It is true that acetate of morphia 
appeared in some experiments to arrest the movements, but the results were not con- 
firmed by the later observations recorded with other solutions of morphia, and never were 
free from certain fallacies which have been mentioned. Whether alcohol or cantharides 
quicken these movements or not must also remain in some doubt, as the results obtained 
were not sufficiently marked to justify a positive assertion, and some fallacy might exist 
due to the currents which occur during the mixture of spirit with water. 
b. Galvanism . — The effects of the application of galvanic currents to these eggs are 
like those already mentioned, as seen in the ova of Gasterosteus. 
c. Heat . — Eggs nine hours after fecundation, when they are cleaving and actively 
contracting, warmed on the stage of the microscope to about 80° F., became still, or 
nearly so, and the oil-drops were a little displaced. At the temperature of the room 
(58° F.) they did not soon recover, but ultimately they cleft, although irregularly. Eggs 
at the same stage, gently warmed to about 70° F., moved much more quickly; on being 
cooled to about 40° F. the contractions ceased entirely ; warmed again, the vivid move- 
ments returned, cooled again, they ceased : left at 60° F. until the next day, the impreg- 
nated ova were seen cleaving, the barren ones contracting, their proligerous disks being 
detached. In these experiments the temperature stated is only approximative, as a ther- 
