44 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the direction and nature of the nuclear division ; in other words, the 
differentiation of the cell-substance shows itself in certain cases markedly 
dependent on the nucleus. In abnormal cases of modified frog ova the 
nucleus shows a striking independence of the cell-substance. The seg- 
mentation nucleus of the punctured half of the ovum may divide repeat- 
edly and change qualitatively although the yolk takes no share. The 
nuclei may cause a series of cytoplasmic changes, far from normal, in- 
deed, eventually pathological. 
Nucleus and Protoplasm.* — Dr. M. Heidenhain has made his ob- 
servations chiefly on sections stained with acidified Ehrlich-Biondi’s 
mixture. He found in the cell-nucleus, in addition to the chromatic 
framework and the nucleoli, a chromophilous substance which he calls 
Lanthanin. This is deposited in the form of small spheres of closely 
webbed fine threads which are made visible by being stained with 
rubin. 
Ho finds that the centrosomes in cells with resting nuclei are always 
double, that the attraction-sphere surrounding is sharply separated from 
the rest of the protoplasm by Van Beneden’s granular stratum, and 
that, in many cases, a radiate structure can be distinctly made out. In 
the rest of the cytoplasm there appears to be a filamentar structure, and 
most filaments can be more or less distinctly seen to be made up of 
separate microsomes. 
Structure of Reticulated Tissue.f — M. L. Demoor finds that the 
structure of adenoid tissue is always the same, whatever be the organ in 
which it is studied. It is formed by the anastomosis of cells provided 
with prolongations, and these cells, both in their nucleus and their pro- 
toplasm present characters which are sufficiently constant to allow, in 
most cases, of the differentiation of the elements enclosed in the network. 
Beside these characteristic elements, other cells (polycaryocytes and 
megacaryocytes) may come into relation with the plexus by their pro- 
longations, and so contribute to its extension. The development of the 
reticulated framework may be effected by direct division of the cells 
which constitute it. All the varieties of leucocytes as yet described may 
be met with in the meshes of adenoid tissue. The giant-cell with bud- 
ding nucleus is not a characteristic of hsematopoetic organs, for it may 
be met with in the lymphatic ganglion of young animals. 
Behaviour of Pigment-Granules during Karyokinesis.J — Dr. J. 
Nusbaum in studying embryos of the frog observed in many ento- 
blast and mesoblast cells an interesting distribution of the brownish- 
black pigment-granules. During the spindle stages the granules are 
mostly peripheral, but as the daughter stars diverge they collect in 
the equatorial plane, forming first a ring, then a disc, and then a 
thick plate. In the middle of this plate a thin unpigmented space 
appears, and the granules diverge towards the poles. Finally, the 
original distribution throughout the plasma is restored. Nusbaum com- 
pares the formation of the equatorial plate to Flemming’s “ Zwischen- 
* Festschrift zum 50-jahrig. Doctorjubilaum von v. Kolliker, Leipzig, 1892, 
pp. 111-66 (3 pis.). See Bot. Centralbl., lv. (1893) pp. 156 and 7. 
f Arch, de Biol., xiii. (1893) pp. 1-40 (2 pis.). 
X Anat. Anzeig., viii. (1893) pp. 666-8 (5 figs.). 
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