vii PRACTICAL DIRECTIONS 393 



the other ganglia supplies one segment (with its appendages) only, 

 except in the case of the last or 6th abdominal ganglion, which 

 gives off nerves to the telson. (The small anterior visceral nerve^ 

 arising from the brain and cesophageal connectives, and supplying the 

 fore-gut, will have been removed ; the posterior visceral nerve, supply- 

 ing the hind-gut, arises from the last abdominal ganglion.) Sketch. 



3 Tease up a ganglion in salt-solution, stain, and examine for 

 nerve-cells. 



V. The antennary or green-glands are situated just behind the bases 

 of the large feelers. Blow through the renal aperture of one side (p. 388) 

 and note the duct and urinary bladder on the dorsal side of the gland. 

 Then cut through the duct, remove the whole gland, and examine under 

 water. Sketch. 



D. The Appendages. Remove the appendages of one side, 

 beginning with the last, one by one, cutting through the articular 

 membrane with a scalpel, and then taking hold of the basal joint with 

 the forceps and pulling the appendage away. Work through the de- 

 scription on pp. 364-367 and sketch typical appendages from each region. 

 Note the delicate paragnatha behind the mouth and the labrtim in 

 front of it (p. 370). 



Procure some pond- water containing specimens of the small " water, 

 flea " known as Cyclops, which will be recognised by its pear-shaped 

 body, and by the two oval egg-sacs of the female. Examine drops of 

 this water until you find some nauplius- larva- of Cyclops, noting the 

 three pairs of appendages and the median eye (p. 384 and Fig. 100). 



The arrangement of the joints and muscles of the limbs can be well 

 seen by examining the large first leg, or cheliped. Note that each joint 

 works in a different plane, and then cut away the exoskeleton 

 from one side of the two or three distal podomeres, so as to expose 

 the muscles (compare Fig. 92). Then remove these, and note their 

 chitinous tendons. Observe that the adductor muscle and its tendon, 

 which closes the pincers, is much larger than the abductor muscle. 



E. Sensory Organs. 



1. Tactile organs. Snip off some setae from the body or appendages, 

 and examine under the microscope. Sketch. 



2. " Olfactory"" organs. Examine the outer flagellum of the 

 antennule under the low power, and. note the tufts of spatula-like 

 ** olfactory " seta on the ventral surface. Sketch. 



3. "Auditory" organ (statocyst}. Carefully cut away the convex 



