632 THE ETOMOSTRACA. 



from the body. More and more followed, until twenty had made their appearance. 

 Thinking that he had taken up a dead specimen, he put it down again, and was hardly 

 less surprised to see it run off quite briskly. 



The substance of the Sea-slater is rather softer than that of the common woodlouse. 

 It appears to feed either on animal or vegetable substances, and is itself much preyed 

 upon by birds and other enemies. The fish are very fond of these creatures, and some 

 species have been known to hover about rocks during a storm for the purpose of prey- 

 ing on the Sea-slaters that are washed into the water. The color is very variable, but 

 is mostly some shade of brown or gray. This, as well as the succeeding species, be- 

 longs to the family of Oniscidae. 



FIG. G in this illustration represents the WATER HOG-LOUSE, a creature that is the 

 aquatic representative of the sea-slater just described. This species is plentiful in fresh- 

 water, whether still or running, and in general walks very leisurely, though when alarmed 

 it can run swiftly. In this genus the proportion of the sexes is reversed, the male 

 being larger than the female. Its average length is about half an inch. 



AT figs. C and D are shown two views of the common WOODLOUSE, the latter figure 

 being given in order to show the equal development of the legs. This creature is very 

 plentiful in all damp places, and especially exult in getting under logs of wood or 

 decaying timber. In cellars and outhouses they are common, and are generally to be 

 found in dark and damp localities. Fowls are very fond of them, and there is no surer 

 way of extirpating these sharp-toothed creatures than by allowing some fowls to scrape 

 and peck about in the places where they have taken up their residence. Under the bark 

 of dead and decaying trees is a very favorite residence with the Woodlouse, and in such 

 localities their dead skeletons may often be found, bleached to a porcelain-like whiteness. 



The color of the Woodlouse is a darkish leaden hue, sometimes spotted with white. 



An allied species, the LAND-SLATER (Oniscus asellus), is equally plentiful. This spe- 

 cies may be distinguished by the two rows of yellow spots and the same number of white 

 spots that run along the back. There are also eight joints in the outer antennae, whereas 

 there are only seven in the same members of the woodlouse. 



THE well-known PILL-WOODLOUSE, or PILL-ARMADILLO, is seen at figs. E and F, the 

 former representing the creature as it appears while walking, and the other shows it 

 when rolled up into a globular shape. In this attitude, it bears a strong analogy to the 

 common hedgehog, and a still stronger to the manis, as in the latter case the creature is 

 defended by horny scales that protect it just as the external skeleton protects the 

 armadillo. While rolled up this creature has been often mistaken for a bead or a berry 

 from some tree, and in one instance a girl, new to the country, actually threaded a 

 number of these unfortunate crustaceans before she discovered that they were not beads. 



As they bear such a resemblance to pills, they have often had to pay the penalty of 

 their likeness ; for in the earlier days of medicine, and even up to the present time, they 

 have been employed in the pharmacopoeia. Even now, though no modern physician would 

 prescribe them for the cure of any disease, the Pill-woodlice may be seen in the recesses of 

 druggists' shops. I have often seen a drawer half-filled with these creatures, and used 

 to convert them into marbles, bullets for a toy cross-bow, and various other purposes 

 in which they were quite as useful as if they had been employed according to the original 

 design. The color of the Pill-woodlouse is dark grayish brown, with a slight polish. 



WE now enter upon a large subdivision of the Crustacea, called scientifically the 

 Entomostraca, a term derived from two Greek words, the former signifying an insect, and 

 the latter a shell. All these strange creatures are aquatic, and their bodies are protected 

 by a shell of horny or leathery consistence, sometimes in one single piece and. sometimes 

 formed of several portions. The gills are attached to the feet, or the jaws and the feet 

 are jointed and fringed with hairs. 



In the first section of these creatures the gills are attached to the feet and they are 

 therefore termed Branchiopoda, or gill-footed. They all swim freely in the water. The 

 first order, the Phyllopoda, or Leaf-footed Entomostraca, have the joints of the feet flat, 



