90 NOTES ON 
displayed when the creature is well fed, and a 
pulsatory motion is observable along the back. 
The head is broad, and has a cluster of small 
eyes embedded on each side. These eyes are 
jet black, set in a dead-white socket. In the 
species at present under our notice, the cluster 
is circular, but in the Gammarus locusta they 
are arranged in a lunate form. The antenne 
are four in number, and are inserted in pairs. 
The three basal articulations are larger than the 
others, which are short and numerous; their 
inferior side is studded with a row of fine 
bristles, which, ordinarily, appear single, but 
when viewed under a lens of one-tenth of an 
inch focus, are found to consist of clusters of 
three each, of unequal length. The legs are 
fourteen. In plate 10, which represents a side 
view magnified, only seven are shown, the 
others being omitted, to prevent confusion. 
They are furnished at their insertion with lami- 
nated plates (cox), whose structure is worthy 
of examination, and requires a good microscope 
and careful management to develope. They are 
transparent, having their inner surfaces covered 
with rows of bent spines, which, viewed in some 
positions, appear like lines; in others, like dots. 
The first four legs are monodactyle, and increase 
