In the first, a cleavage follows each nuclear division; in the second, the nuclei multiply by division a number of times, and then the ovum divides into as many blastomeres as there are nuclei present.
The cells concerned, like all secreting organs, have abundant protoplasm with large nuclei, and sometimes, in addition, part of the cell-wall is modified as a filter.
They possess a delicate Laticiferous layer of protoplasm, with numerous small nuclei lining Tissue the walls, while the interior of the tube (corresponding with the cell-vacuole) contains a fluid called latex, consisting of an emulsion of fine granules and drops of very various substances suspended in a watery medium in which various other substances (salts, sugars, rubber-producers, tannins, alkaloids and various enzymes) are dissolved.
The food so absorbed passes to the outer cortical mycellum, and from this tc the inner hyphae, which appear to be the organs of the interchangi of substance, for they are attracted to the neighborhood of thi nuclei of the cells, which they enter, and iii which they form agglom erations of interwoven filaments.
The cells in which the fungoid organism is vigorously flourishing are exceedingly active, showing large size, brilliant nuclei, protoplasm and vacuole, all of which give signs of iptense metabolic activity.
The protoplasm of a living cell con.sists of a semifluid granular substance, called the cytoplasm, one or more nuclei, and sometimes centrosomes and plastids.
Here structures have been observed which resemble nuclei in some of their characteristics.
B~it the staining reactions of nuclei may vary at different stages of their development; and it i~ probable that there is no method of staining which differentiates with certainty the various morphological constituents of the nucleus.
1.Reconstruction of the daughter nuclei of Phaseolus.
2, L), a nucleolus appears, a nuclear membrane is formed, and daughter nuclei are thus constituted which possess the same structure and staining reactions as the mother nucleus.
This is a necessary consequence of the fusion of two nuclei in fertilization, unless the chromosomes are to be doubled at each generation.
The second ~r hoinotype division which immediately follows reverts to the normal type except that the already split chromosomes at once separate to form the daughter nuclei without the intervention of a resting stage.
In the higher plants, after the separation of the daughter nuclei, minute granular swellingc appear, in the equatorial region, on the connecting fibres which still persist between the two nuclei, to form what is called the cell-plate.
In a few cases both among the higher and the lower plants, of which the formation of spores in the ascus is a typical example, new cells are formed by the aggregation of portions of the cytoplasm around the nuclei which become delimited from the rest of the cell iontents by a membrane.
In Fucus and allied forms the spindle-fibres between the daughter nuclei disappear early and the new cell-wall is formed in the cytoplasm.
The outer protective walls of the oospores of some Fungi are formed out of protoplasm containing numerous nuclei, which is at an early stage separ~t~d from tl-,c. r,rofc,nI,,,zm of ih,~ o,~nor~ T,.
Reduction in size is due to A, Two vermiform nuclei in the emthe absence of cytoplasm, bryo sac; one approaching the eggwhich is in some cases so nucleus, the other uniting with the 11 ~ ~h ~h upper polar nucleus.
Complete sexual differenti- C, Fusion of the germ nuclei in the ation the egg-cell is quies- egg-cell.
In plants with multinucleate cells, such as Albugo, Peronospora and Vaucheria, it is usually a uninucleate cell differentiated by separation of the nuclei from a multinucleate cell, but in Albugo bliti it is multinucleate, and in Sphaero plea it may contain more than one nucleus.
The union of the germ nuclei has now been observed in all the main groups of Angiosperms, Gymnosperms, Ferns, Mosses, Algae and Fungi, and presents a striking resemblance in all.
Doncaster (1906-1907) on the eggs of sawflies, the number of chromosomes is not reduced in parthenogenetic egg-nuclei, while, in eggs capable of fertilization, the usual reduction-divisions occur.
The segmentation of the fertilized nucleus results in the formation of a number of nuclei which arrange themselves around the periphery of the egg and, the protoplasm surrounding them becoming constricted, a blastoderm or layer of cells, enclosing the central yolk, is formed.
Nuclei are everywhere present.
True ring systems, which possess the characters of organic nuclei, do not come into existence in threeand four-membered rings, their first appearance being in penta-atomic rings.
As before, only true ring nuclei, and not internal anhydrides of aliphatic compounds, will be mentioned.
They are not green like the pines, nor gray like the stones, nor blue like the sky; but they have, to my eyes, if possible, yet rarer colors, like flowers and precious stones, as if they were the pearls, the animalized nuclei or crystals of the Walden water.