PRESERVATION OF INVERTEBRATA. 23 
mens. Afterwards treat as above with alcohol of gradually in- 
creasing strength. Professor Hutton tells us that he has made 
a very successful preparation of a Medusa, retaining the natural 
colour, in the following way :—Make a mixture of I part of 
glycerine and 2 of water, and add a little alum and saltpetre. 
Dilute some of this fluid in a jar with an equal volume of water, 
and place the specimen in the diluted liquid. When the Medusa 
hassunk tothe bottom, add, little by little, more of the stronger fluid 
until it reaches the proportion of about 1 of glycerine and 3 of 
water. Probably this method, or some modification of it, will be 
tound to be of wide application to many delicate organisms, 
as glycerine often preserves animal colours in a very perfect man- 
ner, alcohol, chromic and picric acids, &c., completely discharging 
them. For histological purposes, however, this method would 
probably be of little value. 
ACTINZOA.—It is very difficult to kill sea-anemones in 
the expanded condition. One method is to invert over a specimen 
expanded in sea water a tumbler or beaker, and then to pass up 
into the air space above the water fumes of tobacco, through a 
bent glass tube. Another plan is to stupify slowly by adding 
alcohol or potassium bichromate, drop by drop, to the water 
containing the specimen. When quite dead treat with chromic or 
picric acid for about 3 hours,and afterwards with alcohol as above. 
ECHINODERMATA (Starfish, sea-urchins, &c.).—Alcohol, 
about 70 per cent, for a day or two; then strong alcohol, changed 
once or twice in the case of large specimens. In the case of 
large sea-urchins, a small hole should first be made in the test 
with a file, so as to allow the spirit to penetrate to the inside. 
Chromic or picric acids are not applicable in this case, because of 
their decalcifying properties, thatis, unlessthe specimensarewanted 
for section cutting, in which case they should be placed in a com- 
paratively large quantity of chromic acid until all the carbonate of 
lime is dissolved out, and then transferred to alcohol, which must 
be changed several times. I find, however, that the small 
Flolothurian Chirodota of Dunedin Harbour is best preserved by 
placing it alive into picric acid, and removing as soon as it ts 
dead into alcohol. This does not give the weak acid time to 
dissolve the spicules to any appreciable extent. 
TURBELLARIA (Planarians, &c.).—Place alive into “ Lang’s 
fluid,” made of 100 parts of water, 15 of corrosive sublimate, and 4 
of concentrated acetic acid; in half-an-hour transfer to 70 per cent. 
alcohol; change several times, and finally place in strong alcohol. 
ANNELIDA.—Picric acid or potassium  bichromate, fol- 
lowed by alcohol of gradually increasing strength. 
PoLyzoa.—Alcohol 70 per cent. for a day or two, and 
then strong aclohol. 
, CRUSTACEA.—For large specimens with calcified exoskeleton 
(crabs, crayfish), use strong alcohol if it is desired to preserve the 
internal structure. If wanted only for the exoskeleton, place in 
equal parts of glycerine and water containing a little alum and 
corrosive sublimate, first removing as much as possible of the 
soft parts through small apertures made in the joint-membranes. 
