314 
GAMMARIDiE. 
last pair of caudal appendages seems to be a special 
structure, having for its object the antenna-like use of a 
delicate apparatus at the extremity of the body, in the 
same way as the conical appendages at the extremity of 
the body of the Orthoptera are developed in the mole- 
cricket into a pair of elongated setose filaments. If the 
Niphargus were simply a modified Gammarus— which has 
two equal-sized branches to each of the same pair of 
caudal appendages — one cannot understand why both the 
branches should not have been equally increased, instead 
of one being almost obsolete and the other immensely 
developed as it is in Niphargus , or why it should obtain 
an additional joint. It would be easy to say, that as the 
mole-cricket has only need of two anal feelers, the Ni- 
phargus requires only two, and therefore that one of the 
branches in each pair of the Gammarus has become de- 
veloped by use, and the other obsolete by disuse ; but as 
the Niphargus has four frontal antennae, whilst the mole- 
cricket has only two, the former should use four anal 
feelers instead of two. We must here also allude to the 
excellent manner in which Hosius combats the opinion 
of M. Gervais, that this species is only a variety of his 
Gammarus pulex which has remained in a state of imper- 
fection from dwelling in deep dark wells. 
Although we can find no fresh-water ally to this 
genus in the rivers and streams of Europe, yet Bruzelius 
has taken in the deep sea, near Bohusia, a form which 
he has described under the name Eriopis elongata , 
approximating so nearly to it that it appears to be 
scarcely generically distinct. 
We are inclined to think that Gammarus pungens of 
Milne Edwards, from the warm springs of Cassini in 
Italy, also belongs to this genus. 
