The works of Francis Maitland Balfour, Volume 1 (of 4) : $b Separate memoirsBalfour, Francis M. (Francis Maitland)
Science
The works of Francis Maitland Balfour, Volume 1 (of 4) : $b Separate memoirs
Balfour, Francis M. (Francis Maitland)
Embryology; Zoology
With reference to the situation of the cone-like bodies I have described I
have made an observation which appears to me to be of some interest. I find
that bodies of this kind are found in the yolk _completely outside_ the
germinal disc. I have made this observation, in at least two cases which
admitted of no doubt (vide Fig. 7, _nx´_).
We have therefore the remarkable fact, that whatever connection these
bodies may have with cell-division, they can occur in cases where this is
altogether out of the question and where an increase in the number of
nuclei can be their only product.
These are the main facts which I have been able to determine with reference
to the nuclei of this stage; but it will conduce to clearness if I now
finish what I have to say upon this subject.
At a still later stage of segmentation the same peculiar bodies are to be
seen as during the stage just described, but they are rarer; and, in
addition to them, other bodies are to be seen of a character intermediate
between ordinary nuclei and the former bodies.
Three such are represented in Pl. 6, figs. 8_a_, 8_b_, 8_c_. In all of
these there can be traced out the two cones, which are however very
irregular. The striation of the cones is still present, but is not nearly
so clear as it was in the earlier stage.
In addition to this, there are numerous deeply stained granules scattered
about the two figures which resemble exactly the granules of typical
nuclei.
All these bodies occupy the place of an ordinary nucleus, they stain like
an ordinary nucleus and are as sharply defined as an ordinary nucleus.
There is present around some of these, especially those situated in the
yolk, the network of lines of the yolk described by me in a preliminary
paper[82], and I feel satisfied that there is in some cases an actual
connection between the network and the nuclei. This network I shall
describe more fully hereafter.
Footnote 82: _Loc. cit._
Further points about these figures and the nuclei of this stage I should
like to have been able to observe more completely than I have done, but
they are so small that with the highest powers I possess (Zeiss, Immersion
No. 2 = 1/15 in.) their complete and satisfactory investigation is not
possible.
Most of the true nuclei of the cells of the germinal disc are regularly
rounded; those however of the yolk are frequently irregular in shape and
often provided with knob-like processes. The gradations are so complete
between typical nuclei and bodies like that shewn (Pl. 6, fig. 8_c_) that
it is impossible to refuse the name of nucleus to the latter.
In many cases _two nuclei_ are present in one cell.
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