76 NATURE STUDY REVIEW [9 :3— Mar, 1913 



materials, and should have th,e bottom covered with sand or silt, 

 whichever was present in the original habitat. 



Palaemonetes. 

 The shrimp (Palaemonetes, Fig. 4) is most nearly related to 

 the common crayfish of any of the small crustaceans with which 

 this paper deals. The head and thorax are covered by a hard 

 chitonous layer, the carapace, but unlike the crayfish the large 

 pinchers are lacking. Those found in this r,egion are about one 

 to one and a half inches long and usually colorless or a light 

 green color. These shrimps are hard to see in their native habitat 

 because th,ey are so nearly transparent, being almost as clear as 

 the water in which they are found. Palaemonetes is very readily 

 obtained in late spring and summer. They may be se^en swim- 

 ming over the submerged vegetation in water four to five feet 

 deep, where the vegetation reaches close to the surface. They 

 are easily captured with dip, tow, or ordinary minnow nets. 

 Although they may be seen and taken over the vegetation, yet a 

 greater number may be found midway between the surface and 

 bottom among the water plants. Some may be found on the 

 bottom itself. Since the abdomen is well developed they have 

 good powers of springing and readily jump from a shallow net. 

 These shrimps are positive to light of the intensities usually 

 found in nature. Evidently, however, this is not their strongest 

 reaction since they do not crowd to the surface in their native 

 haunts. They are also sensitive to vibrations produced by jar- 

 ring. This reaction is easily observed if the aquarium containing 

 the shrimps is struck lightly, although it is also apparent in 

 natural conditions when th,e water is disturbed. 



The shrimps may be kept in the laboratory in running water in 

 jars containing plants like those of their habitat if the tempera- 

 ture does not greatly differ from that in which they w,ere taken. 

 Sand should be used to cover the bottom of the aquarium rather 

 than silt, although when glass jars are used no bottom covering 

 is needed. These animals are rather hard to keep long in good 

 condition in the school room, because they are more sensitive to 

 changes than either isopods or amphipods. 



EUBRANCHIPUS. 



Eubranchipus or Branchipus (Fig. 5), as it was formerly 

 called, is also known as the fairy shrimp. This common name 

 should not be taken to mean that Eubranchipus is closely allied 

 with the shrimp (Palaemonetes) for the two are really widely 

 separated in their relationships. Eubranchipus is a greenish or 



