A series of stages in the development of the sperm head, showing the various phases in the history of the chromatin nucleolus (n).
Spermatids containing both the chromatin nucleolus (n) and the odd chromosome (x), a the acrosome.
This is probably homologous with the chromatin nucleolus described for the spermatids of the Coleoptera.
With regard to the question of vital form, it cannot be said of the nucleolus that it appears to be an absolute essential, and in a considerable number of young cells it has as yet escaped detection.
I have very rarely met with the condition with the single nucleolus described by Schultz in Torpedo.
Footnote 367: According to Hertwig's most recent statement a nucleolus is present in this nucleus.
In prophase the chromosomes, each now composed of two identical strands called chromatids, shorten by coiling, and the nucleolus and nuclear membrane disappear.
When the nucleus is dividing, the nucleolus disappears.
Cell membrane Cytoplasm Chromatin Mitochondrion Nucleolus Endoplasmic reticulum Nucleus Nuclear membrane The basic structure of a cell is shown in Figure 2.
The nucleolus is a small globular or oval particle, which may be found singly or in numbers in the nucleus, and behaves somewhat differently towards coloring matter than the closely related chromatin.
The nucleolus is especially found in the tissue-cells of the higher animals and plants as an independent constituent; it is wanting in many of the unicellular protists.
Schleiden, whose observations, published in 1838, were made on the cells of plants, believed that within the cell a nucleolus first appeared, and that around it molecules aggregated to form the nucleus.
The granule within thenucleolus or entoblast of a nucleated cell.
If now the cytoblastem is altered by an already formed cell in such a way that a substance is formed that cannot become part of the cell, it crystallises out first as the nucleolus of a new cell.
As a general rule the nucleolus is formed first, and round it by a sort of condensation or concretion the nucleus, which is frequently hollow, and round this again, by a somewhat similar process, the cell.
Originally solid, the nucleus is commonly differentiated later into an outer dense nuclear-membrane and an inner softer or fluid content; either with one single nucleolus or with a variable number of nucleoli.
In addition in each nucleus a nucleolus is visible, and often several or many may be seen (see ss 67 to 70).
Usually the nucleolus has already become flattened into a lentiform shape, and upon its distal face a conical apophysis has been developed, which is divisible into a darker proximal and clearer distal portion.
Figure 106 gives some of the variations in form of the combined nucleolus and element x.
The element x is present, but the nucleolus has disappeared.
In these latter stages the nucleolus has entirely faded out and nothing suggesting an accessory chromosome is present.
Various forms assumed by the combined nucleolus and element x; last figure from a giant cell.
On the behavior of the nucleolusin the spermatogenesis of Periplaneta americana.
In the spermatogonium there is a very large nucleolus (plate I, fig.
Later stages in the development of the spermatozoa, nucleolus grows gradually smaller.
There is nothing in the resting nucleus of the spermatogonia which would suggest either a nucleolus or an accessory chromosome.
In the "bouquet" or "polarized" stage the combined nucleolus and element x are always at one side of the group of loops and down very close to the base of the figure (figs.
The kernel speck, or nucleolus (the so-called germinal spot of the egg).
The small kernel speck or nucleolus (the so-called germ-spot of the egg).
In Amphioxus and Petromyzon there is however but a single nucleolus, and in Mammalia there is usually one special nucleolus and two or three accessory ones.
The nucleus and nucleolus are usually known as the germinal vesicle and germinal spot.
By the action of reagents a nucleolus may be shewn in it.
On one side of the nucleus may usually be seen a large nucleolus (called here, from its lateral position, paranucleus), and the whole nucleus is sharply separated from the surrounding protoplasm by a thin but evident membrane.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "nucleolus" in a variety of sentences. We hope that you will now be able to make sentences using this word.
