480 THE BRINE-SHRIMP. 



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 havebeen 

 employed in the pharmacopeia. 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 a dark grayish-brown, with a slight polish. 



ENTOMOSTRACA. 



WE now enter upon a 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. 



This sub-class embraces a numerous group of small creatures, important as being food for 

 fishes. As parasitic forms they prove considerably injurious to our food-fishes, fastening about 

 the gills, and eventually destroying them. Many inhabit fresh water. 



The well-known Cyclops is an example of one of the principal orders called the Copepoda. 



Many of the species of orders Siphon ostomata and Ostracoda are familiar as parasitic on 

 the sharks, and especially the sluggish molar, or sun-fish. Penella of the latter is large, and 

 has a length of several inches. 



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

 fore 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, leafy, and 

 gill-like, and are fitted for respiration. Sometimes the body is naked, and at best, only the 

 head and thorax are covered with the carapace. The first family of these creatures is the 

 Apodidse, or Footless Entomostraca, so called because all the feet are formed into breathing 

 organs. There are no less than sixty pairs of these feet, all with many joints, and, indeed, the 

 number of joints which are required to form one of these apparently insignificant creatures, is 

 almost incredible. With the wonderful patience of the German nation, Schseffer counted the 

 joints, and found that they fell very little short of two millions. 



One species, the CRAB SHIELD-SHRIMP (Apus cancriformis), is found in Europe. It swims 

 either on its back or in the usual attitude, and uses the branchial feet in its progression. Its 

 food seems to consist of the smaller Entomostraca. The mandibles of this creature are very 

 powerful, and capable of breaking up the shells of the creatures on which it feeds. Its color 

 is brownish-yellow clouded with brown. One species was discovered by Mr. Tuffen West, and 

 named after him. 



A very remarkable being is the BRINE-SHRIMP. It loves to reside in water so strongly 

 charged with salt that every other creature dies in so saturated a solution, about a quarter of 

 a pound of salt being contained in one pint of water. These animals may be seen by thousands 

 in the salt-pans at Lymington, Hants, where the workmen call them Brine-worms. 



They congregate thickly in the strongest brine, while in the ordinary sea-water they do 

 not trouble themselves to venture. The workmen believe that the continual movements of 

 these creatures have the effect of clearing the brine, and if they find that their own salt-pan is 

 without the Brine-shrimp, they always fetch some from another pan. 



The movements of this little creature are most graceful. It mostly swims on its back, its 

 feet being in constant motion, and its course directed by means of its long tail. It revolves in 

 the water, bends itself into varied curves, turns fairly over, wheels to the right or left, and 

 seems thoroughly to enjoy the very fact of existence. Its color is mostly red, and in some of 

 the pans the Brine-shrimps congregate in such multitudes near the surface that the water 

 looks quite pink with their bodies. 



