vii PRACTICAL DIRECTIONS 393 



mandibles and five following pairs of appendages and their 

 segments. Each of 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 oesophageal connectives, and supplying the fore- 

 gut, will have been removed ; the posterior visceral nerve, 

 supplying 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 on 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 description on 

 pp. 364-367 and sketch typical appendages from each 

 region. Note the delicate paragnatha behind the mouth 

 and the labrum in front of it (p. 370). 



Procure some pond-water containing specimens of the 

 small " water-flea " known as Cyclops, which will be recog- 

 nised 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-larvce 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 feeler of the 



