NOTE ON SOME HABITS OF CRUSTACEA. 85 
themselves, came under my notice last summer. Having 
dredged a number of Amphipoda, I placed them in a vessel 
of sea water till I could examine them. Among them I 
noticed what seemed to be a piece of dead weed swimming 
rapidly about and occasionally falling to the bottom. 
Examination with a lens showed that the piece of weed 
was carried by an Amphipod (Atylus swammerdami.), 
which grasped it by the two first pairs of walking legs 
(pereeopoda). When it came to the bottom the animal 
concealed itself beneath the weed, which was much larger 
than itself. 
In connection with this habit of A. swammerdamii, it 
may be mentioned that another species, Atylus falcatus 
-(Metzger), resembles the first named minutely in every 
respect but one, viz. that the first pereeopod has the claw 
(dactylus) immensely developed, while at the base of the 
next joint are two or three strong blunt spines or tubercles 
into which the point of the claw fits. This would appear 
_ to give the latter species a great advantage over its 
congener in grasping an object for purposes of conceal- 
ment. It is a rare species, but I have met with a few 
specimens this summer: I am not aware of its having 
been recorded as British yet. 
In some of the Podophthalmata the same instinct has 
been observed, and especially among the Anomoura. All 
these have the last or hindmost pair of legs of a shrunken 
and apparently almost abortive form. They never appear 
to be used for walking, and are generally carried turned 
up on the back; but they are utilized by some species of 
curiously shaped, flat bodied Crabs (Dorippe) to carry 
the valve of a bi-valve mollusc over their backs, under 
which they can squat and hide. From this it is an easy 
transition through various stages to the Hermit Crabs 
(Paguride), which ensconce themselves altogether in a 
