ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
289 
was suggested by Eismond. It has a double power, attracting in endos- 
mosis, repelling in exosmosis. Its position, combined with the changes 
in osmosis, determines the movements in mitosis. 
Chromatoid Bodies of Sperm-Cells.* — Dr. F. Hermann maintains 
that the stainable granular structures described by Benda and von 
Lcnliossek in sperm-cells have nothing to do with the genuine “ chro- 
matoid accessory bodies ” which represent the centrosome of the sperma- 
tid and give rise to the apical knob of the fully formed spermatozoon. 
Lactation.-j- — Dr. L. Michaelishas studied this in guinea-pig, mouse, 
and cow. From the facts disclosed by a study of the guinea-pig’s mam- 
mary glands, he draws the following conclusions. (1) The change in the 
form of the epithelial cells is partly due to a filling of the alveoli with 
secretion, which causes the cubical cells to flatten ; but the assumption 
of a papilla-like form is quite independent of this. (2) Epithelial nuclei 
pass out into the milk and undergo chromatolysis, helping to form 
casein. They are replaced by direct constriction of epithelial nuclei. 
(3) The leucocytes do not share in forming the milk, though they migrate 
through the epithelium. They grow in the alveoli, and either break up 
there, or take up fat-globules and form colostrum corpuscles. (4) The 
fat of the milk is a true secretion, not a result of epithelial disruption. 
These results were confirmed more or less by the author’s study of mouse 
and cow. 
Composition of Nucleoli.J — M. Aug. Michel finds that the nucleoli 
of Neplithys and Spiophanes consist of two substances, — a main substance 
staining with safranin and carmine, and probably equivalent to pyrrhenin, 
and an accessory substance, perhaps excretory and equivalent to the 
paranuclein of List. 
Cell-Plates and Cell-Plate Rudiments.§ — Herr R. Wolfgang Hoff- 
mann gives a very full discussion of this subject. There is no doubt 
that cell-plates occur very widely among animal cells, but they are very 
variable and rudimentary in character, and have a very subordinate role. 
In a few cases they may prepare the way for cell-division, and may even 
be sufficiently developed to be comparable to those in plants ; usually, 
however, their presence seems more or less indifferent, though they may 
delay the mechanism of division and the final separation of the daughter- 
cells. 
Classification of Forms of Dentine.|| — Mr. C. S. Tomes has some 
critical notes on Rdse’s proposed classification of the forms of dentine. 
Even Rose’s definition of true dentine is open to criticism. True den- 
tine, according to Rose, is a hard tissue with a smooth surface, which 
grows on one side only, and is developed under an epithelial sheath. 
Mr. Tomes shows how this definition breaks down in application, for 
instance, to the teeth of CarcJiaricis and Lamna. 
Canalicuii of Bone-Cells.^— Herr A. Spuler finds that tbe walls of 
the cell-cavities and canalicuii in bone are quite well differentiated, 
* Anat. Anzeig., xiv. (1898) pp. 311-6. 
t Arch. Mikr. Anat., li. (1898) pp. 711-47 (2 pis.). 
t CO. Soc. Biol. Paris, x. (1897) pp. 190-2. See Zool. Centralb!., y. (1S98) 
p. 69. § Zeitschr. wiss. Zool., lxiii. (1898) pp. 379-432 (2 pis. and 7 figs.). 
H Anat. Anzeig., xiv. (1898) pp. 343-8. Tom. cit., pp. 289-92 (2 fig-.) 
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