280 
NOTES AND MEMORANDA. 
‘ The vibrion is killed by the oxygen, and it is only when it is 
in bulk that it is transformed in presence of this gas into cor- 
puscular germs, and that its virulence can perpetuate itself.’ 
Compressed oxygen killing the adult vibrions, 1 have desired to 
know whether it would not also kill the germs by keeping up the 
compression at high tension for a longer time. 
Conclusion : The action of oxygen compressed at a high tension 
and maintained for a long time, acts upon putrefied septic blood in 
the same way as a temperature of 150°. It destroys the vibrions and 
the germs in which the septicity of the liquid is inherent.”* 
Escape of small Animals from Aquaria . — The following simple 
method of preventing small animals which swim about in an aquarium 
being carried away with the water has been successfully employed in 
the zoological station of Naples. The water is conducted away, 
either by a tube proceeding from the bottom of the basin to the 
surface, or by a siphon having the end of discharge bent up again to 
the desired water-level. In order that the small animals may not he 
carried away by the stream flowing through the tube or the siphon, 
these latter are surrounded by a cylinder whose lower end is sunk 
into the sand covering the bottom, whilst the upper end projects above 
the surface of the water. By this means the water is filtered by the 
sand before it reaches the orifice of the tube which draws it off.. As 
regards the width of the cylinder, it is to be remarked that with 
coarse sand and a weak stream it need not be large; on the other 
hand, the stronger the stream is, and the finer the sand, the larger 
ought the cylinder to be, to allow as much water to flow away as is 
introduced in the same time. In applying the siphon as above 
deseribed, it is advisable not to let the end which draws off the water 
reach the bottom of the aquarium, as otherwise sand might be drawn 
up into the siphon, and possibly stop it up. It is sufficient if the 
inner arm reach to the level of the bend in the outer arm.f 
A New Form of Micrometer . — In No. 37 of the ‘Journal of the 
Quekett Microscopical Club,’ Mr. G. J. Burch explains in detail the 
construction and use of a micrometer which he has devised, and which 
he claims to be easy to make and equal in accuracy to all other 
micrometers except the Cobweb. 
The principle on which it is based, is the comparison of the re- 
flection of a scale with the image of the object. It consists of a cap 
fitting over the eye-piece, containing a piece of neutral-tint glass (or 
looking glass, with the amalgam removed in the centre) set dia- 
gonally, so as to reflect to the eye the image of a scale which is 
carried by an arm ten inches long attached to the cap, the object 
being observed through the eye-piece in the usual way. 
To adjust the scale so that it may read decimals of an inch, &c., 
it is moved on the arm nearer to, or further from the eye, till on ad- 
justing the focus so that the apparent distance of the two images may 
* ‘Comptes Rendus,’ vol. Ixxxvii. p. 117. 
t Dr. Spengel in ‘ Zoologischer Auzeiger,’ vol. i. p. 106. 
