DR. W. H. RANSOM ON THE OVUM OF OSSEOUS FISHES. 
493 
by the varying amounts of air in bubbles which entered the cells, and by the accidental 
bursting of the inner sacs in many eggs, a mode of terminating the contractions not due 
to the exhaustion of oxygen, and which is most apt to occur when the proportion of 
water is greatest, provided it be not changed. Nevertheless, in experiment k, with 
thirty eggs in the cell, and imperfect exclusion of air, the contraction ceased in 
twenty-three hours in eggs distant from the air-bubbles, while in experiment j, with only 
seven eggs in the cell, and complete exclusion of air, they continued for twenty-nine 
hours. 
The experiments with impregnated eggs gave more definite results still. For in 
experiment e', with forty-eight eggs in the cell, the yelk-contractions ceased in twenty- 
six hours, leaving the yelk-ball globular and relaxed, while in experiment g', with only 
ten eggs in the cell, they persisted for more than thirty-five hours. 
The pseudo-cleavage, or contractions of the concentrated formative yelk in unimpreg- 
nated eggs, and probably also the concentration of the formative yelk, seem to demand 
the presence of oxygen as well as a due supply of water : for in experiment e, after 
twelve hours it was less advanced than in the ova of control experiment 3. It also was 
shown to cease long before the yelk-contractions, and may be supposed to consume more 
oxygen, although there are other explanations which may be offered of this fact, espe- 
cially the tendency of the matter of the discus proligerus to undergo chemical change 
and disintegration. 
Cleavage may be said to demand more oxygen than do the yelk-contractions, as in ex- 
periments e' to j' it always ceased long before, and was more promptly checked by in- 
creasing the number of eggs in the cell. It is also more quickly arrested than pseudo- 
cleavage, and would seem therefore to need oxygen more. 
Indirectly, bursting of the inner sac and consequent cessation of the yelk-contractions 
depends upon access of oxygen, which acts by favouring decomposition when the water 
is not changed. 
Although some of the changes seen in the eggs in the suffocation experiments may 
be attributed to the poisonous action of some product, and not alone to the absence of 
oxygen, yet the general inference, that oxygen is consumed, is not thereby weakened ; 
and it is a significant and interesting fact, that the cleavage masses in suffocated eggs 
undergo a species of fusion, which much resembles one of the effects of the action of 
carbonic acid on them. 
It remains, however, a weak point, that I failed to obtain chemical evidence as to 
the product of oxidation, which might be expected to be in very small amount, as the 
consumption of oxygen was so minute. 
Despite the difficulties of deciding what interchanges take place between the sub- 
stance of the yelk and the surrounding medium during the functional activity of the 
former, the fact came out with sufficient clearness, that some non-albuminous organic 
matter, and some salts, passed into the water. 
Experiments n to t inclusive, show that cell-multiplication and differentiation, in the 
