276 
ZOOLOGICAL LITERATURE. 
G/'apsus, NautilograpsuSy Sesarma, Lupea, PlatycarcinuSj 
Pilumnus, Chlorodius , Gelasimus, Trapezia ^ CarciauSy and 
Hyas. 
He then enters upon the physiology of the subject, first asking, 
Are crabs conscious of sounds ? and secondly, flow do they hear 
them ? 
Dr. Hensen chiefly performed his experiments on animals 
living in vivaria or in glass vessels, and took every possible care 
to preclude the interference of other phenomena, such as sight, 
&c., with his experiments. And he chiefly preferred to make 
use of such instruments in the production of sound as would 
conduct it into the water. 
Sound made in the air he found to have no effect on animals 
living in the water ; and sound made with a fife or bell in con- 
tact with a membrane connecting the same with the Avater 
produced only weak impressions ; the effect of which was thq^t if 
a peculiar sound was made, the crab would jump at first as if 
from fright, and then quit the place. But these movements the 
animal has the power of controlling, and those which have fre- 
quently been experimented upon are seldom able to be made to 
jump affer the first time. In this way he got mostly negative, 
but also some positive results, which Avere so decided as to 
leave nothing to be desired. 
He has observed young freshly-caught specimens of Palamion 
antennariiis on the first experiment leap out of the water by 
any sound made on the floor, or against the sides of the vessel ; 
but a shaking of the side, unaccompanied by sound, the animal 
took no notice of. Other experiments of a similar character also 
demonstrate that the Decapod Crustacea have the power of 
hearing. 
In order to identify the organs made use of in hearing. Dr. 
Ilensen performed some very interesting experiments with a 
small quantity of strychnine deposited in the water, Avith curious 
results. Under these circumstances, even the slightest sound 
about the house produced marked effects. The animals could be 
made to spring about the vessel in Avhich they Avere ; and it is 
remarkable that, without much trouble, no effect is producible 
on the outer antennae. When the animal has suffered much 
from the strychnine, and is lying upon its side at the bottom 
of the basin, it can be lifted up by the outer antennae Avitli a 
pair of pincers, or the glass may be shaken, without producing 
the slightest effect upon the animal ; but if a sound be produced, 
the creature is immediately excited, and after making a power- 
ful spring, again sinks to the bottom, where it continues in 
strong convulsions. Upon being placed in fresh water (he. in 
marine water without strychnine) it again revives, and soon 
swims about. 
When not in immediate contact with the walls of the vessel. 
