ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
275 
which melts between 50° and 52° C. is better for imbedding than that 
which is harder, for in the latter the embryo may be cracked. 
Sections from 10 to 15 fx thick, and in the oldest stages even thicker, 
are better than those that are very thin. 
Method of observing Asexual Reproduction of Microstoma- 
Dr. F. von Wagner kept his living specimens of Microstoma in small 
breeding aquaria, 15 cm. long, 10 cm. broad, and 6 cm. high ; and he 
did his best to reproduce the natural conditions of their existence with- 
out diminishing the opportunities for observation. A thin layer of mud 
was spread on the floors of the vessels, and food was provided in the 
shape of abundance of Daphnids of various sizes. Only a few plants 
were admitted, and they were, therefore, renewed completely every week. 
Care was taken to prevent the entrance of any other animals. Notwith- 
standing all this care, the specimens did not live for more thau two or 
three weeks. 
The animals, when required for measurement, must be carefully 
drawn out with a pipette, placed in a small watch-glass, and measured 
with an eye-piece micrometer. Great patience is needed. 
Various preservative reagents were tried, and a concentrated watery 
solution of sublimate was found the best. Lang’s fluid and a half per 
cent, osmic acid solution often gave good results. Weigert’s picro- 
carmine was used for staining, and sections 1/100 to 1/500 mm. in 
thickness were cut. 
Examining Bone Marrow for developing Red Corpuscles t— 
Herr E. Neumann says that phases of the development of the red blood- 
corpuscles may be observed by obtaining bone marrow in the following 
manner : — The marrow is squeezed out of some cancellated bone by 
means of a vice, and a small quantity of this taken up in a capillary 
tube and placed on a slide. Having been covered, it is examined directly 
without any addition. By this means good results can be obtained from 
ribs of human bodies which have been dead for some days. 
Study of Contraction of Living Muscular Eihres.J — M. L. Ranvier 
studied the appearances of living striated muscular fibres during stimu- 
lation by an electric current in the following manner : — The retro- 
lingual membrane of the frog is stretched over the platinum ring 
devised by the author, and placed in some indifferent fluid in a moist 
chamber. Before putting on the cover-glass and closing it down with 
paraffin, two strips of tinfoil are placed on the slide in such a way that 
they may serve as electrodes. These movable electrodes receive the 
current from a bichromate battery, the ends of the wires of which are 
surrounded by flat lumps of lead. These rest on the tinfoil. 
Observations carried out in this way show that when a striated 
muscular fibre is stimulated, the striation is present during all stages of 
contraction, and that the contractility of muscle is invariably associated 
with the contraction of the thick discs, which assume a somewhat 
spheroidal shape, the thin discs on the clear spaces being unaffected. 
In a similar way the contraction of unstriped muscular fibre is observed. 
* Zool. Jahrb., iv. (Abth. f. Anat. u. Ontog.) pp. 420-1. 
t Virchow’s Archiv, cxix. (1890) pp. 385-98. See Zeitschr. f. Wiss. Mikr., vii. 
(1890) p. 364. % Comptes Rendus, cx. (1890) pp. 613-7 (2 figs.). 
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