A Phyllopod Crustacean. 93 



The Excretory System. A pair of so-called " shett- 

 glands r may function as renal organs, and have been com- 

 pared with nephridia. They open to the exterior through 

 two papillae, near the bases of the second maxillae. 



The Muscular System is well developed. Observe the 

 extensor and retractor muscles of the abdomen. Also note, 

 in the thorax, the presence of regularly arranged muscle 

 bundles. Recall the arrangement in Nereis. 



The Nervous System. - - Observe the minute, median 

 ocellus. Below and on each side of it are the first antennae, 

 the tactile organs. The compound ? eyes are large and promi- 

 nent. Are they stalked? Examine carefully and note the 

 facets. 



Make a drawing of the head, paying particular attention 

 to the organs of special sense. 



Carefully remove the appendages from another specimen, 

 using a pair of fine scissors. Cut the animal open along the 

 mid-dorsal line, and remove the lateral walls of the thorax 

 and abdomen, together with all but the most anterior portion 

 of the alimentary tract. Wash out the cavity with ninety- 

 five per cent alcohol, and then place in absolute alcohol for 

 one quarter of an hour. Remove from absolute alcohol and 

 place in xylol. The delicate ventral chain of ganglia will 

 soon take on a different appearance from the rest of the 

 specimen. Note that there are two ganglia in each thoracic 

 segment, each connected with its fellow by a cross commis- 

 sure. The ganglia lying anterior and posterior to each other 

 are united by longitudinal connectives. Follow the chain 

 into the abdomen and also anteriorly into the head. As 

 in Nereis, it will be found to surround the oesophagus and 



