KILLING HYDROID ZOOPHYTES AND POLYZOA. 333 
ON SOME EXPERIMENTS MADE WITH A VIEW 
OF KILLING HYDROID ZOOPHYTES AND 
POLYZOA, WITH THE TENTACLES EXTENDED. 
By Herpert C. CHapwick, F.R.MLS. 
OME time ago, having heard that Marine and Fresh-water 
Polyzoa had been successfully killed with the tentacles fully 
extended, by means of a one per cent. solution of osmic acid, 
I determined to try the experiment myself. The subjects of my 
first experiments, all of which resulted in a complete failure, were 
a few specimens of Lophopus crystallinus. 
Shortly after this, a slide was shown to me, on which was 
mounted a specimen of Bugula plumosa, which had been killed 
with osmic acid. The tentacles, though almost fully extended, 
were much blackened by the acid, and did not show much of the 
effects of the picro-carmine stain to which they had been subjected. 
The slide was, therefore, of little scientific value. 
About the same time I subjected a small specimen of the same 
species to further experiment, using absolute alcohol instead of 
osmic acid. The result was a most encouraging success. I then 
experimented with alcohol upon Lophopus crystallinus, and the result 
was several most successful preparations. Further experiments 
upon Bugula plumosa gave various results; in some cases com- 
plete success, in others failure. 
Bugula flabellata was very difficult to deal with, but after half-a- 
dozen attempts, I succeeded in killing a specimen which was shown, 
stained and mounted, at the October meeting of the Manchester 
Microscopical Society. ‘The method employed in every experiment 
is as follows:—Place a specimen of the Polyzoon to be experimented 
upon in a small beaker or clear glass bottle, and allow it to remain 
at rest for several hours. Now take a dipping tube drawn out to 
a very fine point, and charge it with absolute alcohol. Having 
ascertained by means of a pocket lens that the polypides are fully 
extended, allow the alcohol to drop very gently from the point of 
the tube, which should be held just above the surface of the 
water. The success of the experiment depends largely upon the 
care with which the first quantity of alcohol is introduced into the 
water. After the lapse of an hour, if the polypides are still 
extended, a further quantity of alcohol may be added, until the 
quantity reaches 60 per cent. 
After passing through 75 per cent. alcohol, the specimens may 
be kept in 90 per cent. of the same, until required for mounting. 
Experiments with alcohol upon Hydroid Zoophytes were not so 
successful, but Kleinenberg’s Picrosulphuric acid solution, with 
