1895.] Microscopy. 399 
MICROSCOPY.’ 
Preservation of some Marine Animals.—In 1891 there ap- 
eared a paper by T. Tullberg, Veber Konserviering v. Evertebraten in 
ausgedehnten Zustand, in which a novel use of magnesium sulphate, or 
Epsom salts, was described. Tullberg was guided in his researches by 
the a priori ‘edhianeriliah: that, as sea-water contains several salts in 
definite proportions, it is probable that marine animals would not con- 
tract if the proportion of one of the salts was increased, for the animal 
is already accustomed to these substances; and, on the other hand, it 
might have a toxic effect. Experimenting with Actinia, he finds that: 
chloride of sodium has no effect, but with sulphate or chloride of 
magnesium the Actinian expands its tentacles, and after a certain time 
does not contract at all when its tentacles are pinched. He lets the 
Actinian expand in a vessel of sea-water, the quantity being deter- 
mined so that the percentage of the salt added may be known. He 
then adds to the vessel a thirty-three per cent solution of magnesium 
chloride or sulphate until the water contains 1% of the salt. The ad- 
diton is made slowly but is effected within half an hour, at the end of 
which time the Actinian is found to be anesthetized. As a matter of 
fact only the exterior of the animal loses its sensibility. 
It is then necessary to kill the animal which may be done by inun- 
dating it with some killing fluid, but in this case partial contraction 
may take place rendering it unfit for museum purposes. A better 
method is to kill it by slowly adding a 01% solution of chromic acid 
until the water contains from ‘03% to ‘05% of theacid. 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. 
This method was applied successfully to various fresh-water and salt- 
water invertebrates including various Actinians Holothurian, Turbel- 
larians, Nemertines, Cheetopods, Gasteropods, Ciona, ete. ete. 
Last summer, through the kindness of Commissioner MacDonald, I 
had the opportunity of spending a few weeks at the U. S. Fish Com- 
mission laboratory at Wood’s Hole, Mass., and obtained some interest- 
ing results with Epsom salts in the preservation of many of the marine 
invertebrates of that vicinity. The method of application requires 
modification in individual cases but a few experiments will usually en- 
1Edited by C. O. Whitman, University of Chicago. 
