TISOPODS 291 
Genus Caprella 
C. geometrica. These very curious little animals, which are so slen- 
der as to seem like skeletons, are found in abundance clinging to hy- 
droids, Polyzoa, delicate alge, or eel-grass, or under stones in tide-pools. 
They resemble in color, and often in form, the objects on which they 
live. Holding on by the pos- 
terior feet, they extend the body 
out rigidly or sway it about, so 
that they resemble little sticks 
or branches, and often escape 
detection. In walking, they 
bring the hind feet up to the Caprella geometrica, 
front ones, doubling the body 
into a loop like the canker- or measuring-worm. The appendages on 
the anterior and posterior ends are furnished with chele and hooks; 
those of the middle section are rudimentary. This animal cannot be: 
mistaken for any other. C. geometrica is found fiom Cape Cod to North 
Carolina. Some of the species of this genus may be found on every 
coast. 
SUBORDER ISOPODA 
The isopods have an elongate, flattened, but more or less 
arched body, composed of seven thoracic segments and a short 
abdomen of six segments. The six segments of the abdomen 
are smaller than those of the thorax, and are often more or less 
united, sometimes into a single piece with scarcely any trace of 
division above; but the number of pairs of appendages is gener- 
ally six, showing the composite nature of the apparently simple 
organ. The last segment, or telson, is broad and has a pair of 
modified appendages. The seven thoracic legs are not all equal, 
as the name would imply, but vary greatly in different species. As 
a rule, they are adapted to walking or attachment, and in the fe- 
male some have delicate plates which form brood-pouches. The 
swimming-feet fold under the abdomen, and in some species are 
inclosed by the first pair, which are large and plate-like, and form 
a complete cover for the others. The isopods are a large and 
widely distributed order, varying in size, and are inconspicuous 
because they cling closely to objects. They are retiring in habit, 
though extremely ferocious. 
The sow-bugs or pill-bugs, common in gardens, under leaves in 
the woods, and under almost any pile of rubbish among decaying 
vegetable matter, are a land species of isopods. Other species in- 
