ISOPODS 291 



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 algae, 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 chelae and hooks ; 



those of the middle section are rudimentary. This animal cannot be 



mistaken for any other. C. geometrica is found from 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- 



