ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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of weak spirit ; the tadpoles, when taken out of the fishing-net, should 
be dipped head foremost in the tube. On reaching home the liquor 
should be at once changed to spirit 40 over proof, and this must be 
changed daily till it ceases to be strongly coloured. This mode of 
treatment preserves the natural shape of the tadpole, and the delicate 
caudal crests dc not shrivel. Tadpoles should never be allowed to 
remain out of the fluid, as they shrink very rapidly. Chromic acid is 
not to be recommended, as it renders the specimens too brittle for ordinary 
study. 
Preservation of Invertebrates in a State of Extension.* — Herr 
T. Tullberg was guided in his researches by the a priori consideration 
that, as sea-water contains several salts in definite proportions, it was 
probable that marine animals would not contract if one was to increase 
the proportion of one of the salts of the water ; for the animal is already 
accustomed to these substances, and, on the other hand, it might have a 
toxic effect. Experimenting with Actiniae (and especially with Actinoloba 
dianthus) he found that chloride of sodium had no effect, but with 
sulphate or chloride of magnesium the Actinian expanded its tentacles, 
and, after a certain time, did not contract at all when its tentacles 
were pinched. 
It is first necessary to get an Actinian into a state of expansion ; 
this may be done by leaving it for some time, even twenty-four hours, 
in a vessel of sea-water. The quantity of water must be measured so as 
to know the percentage of salt which is to be added. These precautions 
having been taken, a 33 per cent, solution of chloride of magnesium is 
added until the vessel contains 1 per cent, of the salt ; thus for one litre 
of sea-water 30 ccm. of the solution must be added. The addition 
should be made slowly, or even intermittently ; but it must be effected 
within half an hour. Thirty minutes later the animal will be found to 
be anaesthetized. As a matter of fact only the exterior of the animal 
will have lost its sensibility. The animal must now be killed ; if the 
animal be inundated with alcohol, concentrated chromic acid, or 
Perenyi’s fluid the result may be satisfactory for anatomical or histo- 
logical purposes, but the specimens will not be fit for exhibition in a 
museum. If the fluids are added slowly, better results will be obtained. 
With chromic acid the following procedure may be adopted: — a tube 
with a funnel is plunged as far as the bottom of the vessel in which the 
animal lies, and a • 1 per cent, solution of chromic acid is slowly and 
intermittently added. If the animal begins to contract during the 
operation, it must be stopped for a short time. The addition of acid 
must go on until the chromic acid is in the proportion of -3 to • 5 per 
cent, of the total liquid. If the animal does not contract when this 
solution is added, the dose of chromic acid must be increased till the 
proportion is • 5 per cent. 
The results of this method are very satisfactory, save that there is a 
decrease in the volume of the animal. Sections of the tentacles showed 
that the cells were not attacked by the substances employed. Various 
animals have been experimeuted on. The author has applied this pro- 
cess to terrestrial and fresh- water Invertebrates, and finds that chloride 
* Arch. Zoo], Exper. et Gen., x. (1892) pp. xi -xiv. 
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