ON THE PAIRED NEPHRIDIA OF PROSOBRANCHS. 589 
Patella, whilst they only confirm prior investigations as 
regards Haliotis, Trochus, and Turbo. 
I further hope to offer a plausible explanation for the con- 
tradictions between my predecessors and myself, and must add 
that to attain this end I expended more time and trouble than 
it cost me to arrive at the conclusions which I intend to 
describe in this paper. 
Methods employed in the Present Investigations. 
In order to fix the tissues as rapidly and as perfectly as 
possible I made use of the following fluids, viz. Kleinenberg’s 
fluid (picro-sulphuric) with a few drops of osmic acid, and a 
mixture of sublimate and glacial acetic.' The specimens of 
Patella and Fissurella were dropped living into these fluids, 
left there for about a quarter of an hour, then thoroughly 
washed with water, and afterwards hardened in spirit from 40 
per cent. up to 90. I tried Flemming’s fluid (chromosmic 
acetic), but was obliged to discard it, as it made the tissues too 
brittle. When the specimens have been in spirit some time 
they can be easily taken out of the shell by pulling them 
gently with a pair of forceps. They then come out perfectly 
uninjured. 
For Trochus I had to use a different method, as the shell 
and operculum make the animal impervious to the fixing 
liquid. The shell in the species which I investigated is so 
thick and hard that it cannot be removed while the animal is 
living without injuring it severely. I therefore put the 
Trochuses into sea water and 1 per cent. absolute alcohol 
(according to Signor Lo Bianco’s method) in order to draw the 
anterior half of the body out of the shell. After a day or two 
the animals are paralysed without being killed. It is then 
possible to pull the anterior half of the body out of the shell 
and to plunge them into the fixing Jiquid, which can then easily 
penetrate into the shell and the mantle cavity. The specimens 
were then hardened in spirit for a few days. It is then 
1 Sublimate 5 per cent, in sea-water 3 parts, and 1 part of glacial acetic acid, 
