THE ASELLUS. 



125 



THE ASELLUS. 



Haunts. This animal lives amid the submerged plants 

 of our streams and ponds. It is about an inch long, 

 and of a uniform slaty gray or pale-brown color. If plants 

 be drawn out of the water, it will be found clinging 

 to them, and may be picked up with 

 forceps, and dropped into alcohol for 

 preservation. Live specimens should 

 be kept in a glass jar, in water, with 

 aquatic plants, in order that their 

 feeding habits and method of getting 

 about may be studied. 



External Features. Place a live 

 asellus in a watch crystal with water. 

 Add a few drops of chloroform or 

 ether. Observe as to its general form 

 the following points : 



1. A nearly linear body, much flat- 

 tened dorsally. 



2. A distinguishable head, with a 

 pair of sessile eyes, and greater and 

 lesser antennae, easily seen from above. 



3. A long, distinctly segmented thorax, bearing seven 

 pairs of legs. 



4. A short, broad abdomen, with a pair of terminal sty- 

 lets projecting posteriorly. 



As soon as the animal has become quiet, place the watch 

 glass on the stand of the microscope, and with low power 

 (100 diameters) focus upon various parts of the abdominal 

 stylets. They are sufficiently transparent to permit the 

 blood in them to be seen circulating. 



Obtain a specimen which has been a short time in alco- 



ASELLUS. 



