. Cassell's natural history. Animals; Animal behavior. SECOND ORDER III.—ISOPODA (EQUAL-FOOTED). The Isopoda are so named in allusion to the general confoi-mity in size and function of the seven pairs of legs, the two foremost pairs of which in the Amphipoda are equivalent to the two outer pairs of jaw-feet in higher Crustacea. In the Decapoda, Stchapoda, and Amphipoda, the branchiie (in each case) are attached to the base of the legs. In the Isopoda, on the contrary, the posterior (abdominal) appendages are converted into special organs of respiration, in the form of l
. Cassell's natural history. Animals; Animal behavior. SECOND ORDER III.—ISOPODA (EQUAL-FOOTED). The Isopoda are so named in allusion to the general confoi-mity in size and function of the seven pairs of legs, the two foremost pairs of which in the Amphipoda are equivalent to the two outer pairs of jaw-feet in higher Crustacea. In the Decapoda, Stchapoda, and Amphipoda, the branchiie (in each case) are attached to the base of the legs. In the Isopoda, on the contrary, the posterior (abdominal) appendages are converted into special organs of respiration, in the form of leaf-like appendages The heart is also near the tail. The body is composed of seven segments, generally nearly equal in size. To these, in the normal Isopods, seven pairs of nearly uniform legs are attached, either fitted for walking, swimming, or as powerful hook-like organs which enable them to adhere firmly to the fishes upon which many of them are parasitic. One group of Isopods, the Oniscidce, familiar to us in gardens under the name of the Common Wood Louse, are all air-breathers—not residing in water, but in damp situations—breathing air, which, however, it is necessary should be saturated with moisture. Several of the species which inhabit caves are destitute of eyes, , Titamlhes albus, from the Mammoth Cave, Kentucky. The Great Sea-Slater (Lyc/ia oceanica) is common on the British coasts, running with agility, and folding up, so as to feign death, when attacked. One of these, found in some gardens and !, the Armadillo (also named tlie "Pill Bug" in America), from the perfect way in which the .segments roll together, forcibly reminds one of the fossil genus IllcemM barriensis, a Trilobite found in the Upper Silurian at Barr, Staffordshire. Prof Alexander Agassiz, aided by the United States Coast Survey, has carried on extensive deep- sea dredging operations in the American seas, particu- larly exploring the bed of the Gulf Stream and the Straits
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