POISONS. 241 
my experiments lead to no very instructive con- 
clusion, they are, I think, worth stating. 
I first tried dissolving chloride of sodium in fresh 
water till the latter was of the same density as sea- 
water. Sarsiz dropped into such a solution con- 
tinued to live for a great number of hours; but 
they were conspicuously enfeebled, keeping for the 
most part at the bottom of the vessel, and having 
the vigour of their swimming motions greatly im- 
paired. The tentacles and manubrium were strongly 
retracted, as in the case of exposure to fresh water, 
and the tissues also became slightly opalescent. 
Thinking that perhaps a fairer test would be only 
to add as much chloride of sodium to the fresh 
water as occurs in sea-water, I did so; but the re- 
sults were much the same. On now adding sulphate 
of magnesium, however, to the amount normally 
present in sea-water, the Sarsize became more active. 
I next tried the effects of chloride of sodium dis- 
solved in fresh water to the point of saturation, or 
nearly so. The Sarsiz, of course, floated to the 
surface, and they immediately began to show 
symptoms of torpidity. The latter became rapidly 
more and more pronounced, till spontaneity was 
quite suspended. The animals, however, were not 
dead, nor did they die for many hours, their irrita- 
bility continuing unimpaired, although their spon- 
taneity had so completely ceased. The tentacles and 
manubrium were exceedingly relaxed, which is an 
interesting fact, as being the converse of that which 
occurs in water containing too small a proportion of 
salt. Lastly, to give the density hypothesis a still 
