1895,] Microscopy. 401 
ing fluid was applied. Good results were obtained with Cirratulus, 
Amphitrite, Nereis, Rhyncobolus, Clymenella and Phascolosoma. Phas- 
colosoma in most cases was killed with tentacles protruded. Nemertean 
worms, when transferred to a killing fluid before being completely 
narcotized, sometimes protruded their probosces. 
ASCIDIANS.— Molgula and Cynthia were readily killed with siphons 
open after anzesthetization with magnesium sulphate. In this case it 
is best to add the saturated solution of sulphate intermittently with a 
pipette. 
CrenopHores.—After considerable experimentation a method for 
preserving these delicate creatures in a nearly life-like appearance was 
devised. Formalin alone in solutions of varying strength had been 
tried without success. It was found necessary to treat the animals 
with some hardening reagent before placing them in the formalin and 
the following method seems to be the most successful. To a solution of 
equal parts of 2% formalin and Perenyi’s fluid was added enough 
common salt (NaCl) to increase the density of the mixture to that of 
sea-water, i. e., until a Ctenophore placed in it barely floated. This 
adjustment of the density of the surrounding medium prevented the 
Ctenophores from collapsing of their own weight. After remaining for 
about half an hour in this fluid, they were transferred to 4% formalin, 
the density of which had been increased by the addition of either 
Epsom salts or common salt so that the Ctenophores again barely 
floated. Epsom salts is probably better than common salt for increas- 
ing the density of the fluid. Some specimens which were preserved 
in formalin-+-NaCl began to shrink after a few days, while some 
(Mnemiopsis) which have been preserved for nearly six months in for- 
malin-+ MgSO, are still in excellent condition. 
After the Ctenophores have been properly preserved, precaution must 
be taken in transporting them, for they are easily torn to pieces. If 
they are placed in bottles filled with fluid of the proper density and the 
cork so inserted as to leave no air bubbles, this danger is reduced to a 
minimum.—-W. A. REpENBAUGH, Dartmouth Coll., Hanover, N. H. 
