ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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have arrived at conclusions that have differed so widely from each 
other.” At the end of the section on the effect of curvature, the author 
dismisses Haycraft’s theory that the optical striping is due to the vari- 
cosities of the fibrils. The next part of the paper deals with the 
appearances of muscle in polarised light. We are not able to do more 
than refer to the general contents of Prof. Rutherford’s paper, which 
is very beautifully illustrated. The author supports the fibrillar theory, 
and is in harmony with Kolliker, Merkel, Fredericq, and Rollett. He 
entirely disagrees from the opinions of Krause, Engelmann, Klein, 
Marshall, Melland, van Gehuchten, and others who have advocated the 
doctrine originally started by Bowman, that the fibrils result from post- 
mortem cleavage of the sarcous substance. 
Cells and Energids.* — Prof. A. von Kolliker says that muscle-fibres 
must be looked at in two ways ; — on the one hand as a sum of energids, 
in so far as their nuclei and the sarcolemma are direct products of the 
original uninucleate muscle-energids ; and on the other hand as allo- 
plasmatic structures as regards their muscle-fibrils. Similarly, but with 
less certainty, the axis-fibrils and their continuations into the cell-body 
of the neurodendrites may be regarded as alloplasmatic, while the 
neuroplasma in the cell-processes and cell-body are remains of tho 
energid. Nissl’s bodies and the medulla may be regarded as passive- 
energid products or u ergastic ” structures in Meyer’s sense. The 
author will not, however, admit the generality of the statement that 
passive energid products are unorganised, and grow only by apposition 
(Sachs and Meyer). 
Centrosomes in Ganglion and Cartilage Cells.j — Prof. J. Schaffer 
describes the occurrence of centrosomes in the peculiar cells of the 
lingual cartilage in Myxine glutinosa, and in the cerebral ganglion-cells 
of Petromyzon Planeri. 
Conditions of Cell-Division. J — Prof. Th. Boveri brings together the 
general results of his detailed work in a discussion as to the physiology 
of cell-division. His general conclusion is stated as follows : — “ To 
bring the protoplasm into the disposition requisite for cell-division, it 
is not enough that nuclear substance should be present, nor that the 
nucleus should be in a certain state ; it is necessary that the nuclear 
substance enter into definite relations with the poles, which must be 
regarded as the centres of the division-process.” 
Formation of Skin-Pigment. § — -Herr B. Rosenstadt begins'! his 
paper by discussing the two opposed views : — (1) That melanotic pig- 
ment is derived from the blood ; and (2) that the pigment is due to the 
metabolism of the skin-cells. In 1893, he gave some arguments in 
support of the view that pigment might be formed in the epidermic 
cells themselves ; and distinguished cases of this as pigment-degeneration 
from other cases of apparent pigment-infiltration. A prior question, 
however, is as to the nature of the melanotic pigment ; and, although we, 
* Verh. Anat. Ges. in Anat. Anzeig., xii. (1897) Erganz.-Heft, pp. 21-5.. 
t SB. Akad. Wis3. Wien, cv. (1896) pp. 21-8 (1 pi.), 
i SB. Phys.-med. Ges. Wurzburg, 1896, pp. 133-51 (5 figs.). 
§ Arch. Mikr. Anat., 1. (1897) pp. 350-81. 
1897 2 a 
