[39] THE PRESERVATION OP MARINE ANIMALS HOVEY. 



Ciona intestinalis is killed slowly by putting into the water in wliicli 

 the animals have expanded a few droj)S of the chrom-acetic mixture 

 No. 2. When the animal has died, which happens in about a half hour^ 

 it is to be taken by the anterior orifice, to avoid the discharge of the 

 water within, and put into chromic acid of 1 per cent, making an injec- 

 tion of the same into the body cavity. The transfer to the alcohol 

 series should be made in the same way. 



Certain ascidians {Ascidia and Bhopalea) are killed in the following 

 manner, so as to keep the orifices open: They should be placed in 

 beakers Avith from 4 to 5 cm. (about 2 inches) of sea water above 

 them. Then slowly drop in 1 per cent chromic acid in such a manner 

 as to form a stratum on the top of the water. Little by little the 

 chromic acid will diffuse through the water, usually killing the animals 

 in from twelve to twenty-four hours. If the animals are not dead by 

 that time, add a little more chromic acid. Harden in chromic acid of 1 

 per cent, wash in fresh water, and put into alcohol. The animals should 

 not rest against the sides of the beaker during narcotization. If the 

 animal has not a good base upon which to stand, some clean sand may 

 be placed in the bottom of the glass, in which it can be arranged in the 

 desired position. 



Molgula, Polycarpa, Rhopalea, and Chevreulius (BJiodosoma) must 

 remain for twelve hours in chloral hydrate of 0.1 of 1 per cent. Then 

 kill them in chrom acetic No. 2 and transfer at once to 1 per cent 

 chromic acid for a little time to harden. 



Cynthia and Styela are narcotized in 0.2 of 1 per cent chloral hydrate 

 for twenty-four hours and then treated like the last-mentioned genera. 

 Cynthia papulosa, however, sometimes contracts greatly when immersed 

 in chloral hydrate of 0.2 of 1 per cent. When it does, put it back into 

 running sea water to expand again, and then try treating it with 0.1 

 of 1 j)er cent chloral hydrate. 



Ascidice compositce. — The gelatinous forms — for example, the Botryl- 

 lidse, Polyvyclus, Circinalium, and Fragarium — are allowed to lie in chlo- 

 ral hydrate of 0.1 of 1 per cent for a few days and then are killed by 

 pouring hot saturated sublimate over them. Immediately afterwards 

 they are transferred to chromic acid of one-half of 1 per cent, where they 

 are left for a half hour before they are washed and transferred to alcohol. 



Distaplia^ after it has been narcotized with 0.1 of 1 per cent chloral, 

 is killed with chrom-acetic No. 2, washed, and put directly into weak 

 alcohol. 



Diazonaviolacea should remain twelve hours in chloral hydrate of 0.2 

 of 1 per cent, and then the killing and the hardening should be done as 

 with the Botryllidse, except that the individual animal should be injected 

 with the liquid. Small colonies may be killed in acetic acid and hard- 

 ened in one-half per cent chromic acid. 



Leptoclinum and other forms of a certain consistency are transferred 

 from the chloral directly to the alcohol. 



