HE. W. H. EANSOM ON THE OVUM OE OSSEOUS FISHES. 
495 
only physical services to the organism, and then they are generally marked by singular 
stability. 
The inner sac is to be looked on as the homologue of the primordial utricle, and its 
thicker portion with the granules of the discus proligerus would then correspond to the 
granular mass around the nucleus in the plant-cell. 
The food-yelk is held to be the equivalent of the fluid cell-contents, and the germinal 
vesicle and spots hold the position of the nucleus and nucleoli. 
Contractility, which there is some reason to think is a property common to all cell- 
contents or protoplasm, in the egg, as in Tradescantia, appears to have its seat in the 
surface-layer. It may be spoken of as of two kinds, Rhythmic and Fissile. 
The former is met with, at least in the egg, as in very many other cells, in a portion 
only of its life-history, and varies very much as to the vividness of its manifestations in 
different organisms. Its essential conditions do not appear to differ from those which 
govern all other known vital actions, and its normal excitors are the same as those of 
higher motor structures, but it seems to be less liable to be influenced by most poisons 
than are the vital properties of higher tissues. It is not influenced in any manner by 
the spermatozooids. From the contractile matter of striated muscle it differs in one 
important particular, viz. that while the former is permeated by an alkaline fluid it is 
bathed with an acid. No explanation of its rhythmic character has yet been found, 
and its uses in the economy are also unknown. In the ova of osseous fishes, and in those 
of Batrachia, its existence has been ascertained, but usually its manifestations are slow and 
indistinct. That the rhythmic contractions have no essential relation to growth in the 
ovum of osseous fishes, is shown by the fact that they do not begin until the egg has 
reached its full size. I venture to suggest that they may be connected in some way 
with the conversion of a lower form of organic matter into a higher, such as occurs 
when food-yelk is transformed into formative yelk. It seems probable that the excep- 
tional vividness of the contractions noted in some fishes, as the pike and the stickle- 
back, is connected with the rapidity of the changes which take place in the egg. 
These eggs hatch in a shorter time than do those in which the contractions are slow 
and indistinct. Were it not for their orderly recurrence, one might be tempted to 
refer them to the same category as those motions which occur during the admixture of 
certain fluids, as of spirit and water. 
The fissile contractility is also independent of the action of a male element, although 
so far influenced by fecundation as to owe persistence and regular progress to it. Its 
essential and modifying conditions are otherwise like those of the rhythmic con- 
tractility, but its normal excitors, if we except heat, are but little known. It requires 
for its maintenance that a portion of the lower form of protoplasm united with oil shall 
be continually converted into the higher. Its results are growth and development. 
To show the extent and importance of the question as to the nature and properties of 
protoplasm, I will draw a brief parallel. The first germ of an animal, as the egg ; the 
first stages of organic matter about to be formed into tissue in the body, as the white 
mdccclxvii. 3 x 
