414 APPENDIX. 



body, the bristles on the ventral side, the orifices — mouth, re- 

 productive, and anal — also the dorsal pores along the middle 

 line of the back. Note the red line which marks the course of 

 the dorsal blood-vessel. To examine the internal anatomy, lay 

 the worm in a dish having a layer of beeswax in the bottom, 

 slit open the body along the middle line of the dorsal surface, 

 and separate the muscular walls of the body from the parts 

 lying within, fastening back the flaps by pinning them to the 

 beeswax. Keep the specimen covered with water if the worm 

 he freshly killed, or with fifty per cent, alcohol if it be a pre- 

 served specimen. Note the membranous partitions which sub- 

 divide the. large cavity of the body: the dorsal blood-vessel, 

 lying along the top of the digestive system, around the anterior 

 part of which are circular blo6d-vessels ; the digestive system, 

 consisting of the following principal parts : pharynx, gullet, 

 crop, stomach, intestine, and along the top of the latter the so- 

 called " liver." Along the sides of the anterior part of the di- 

 gestive system look for the oesophageal glands and the repro- 

 ductive glands. Slit open the alimentary canal and study its 

 structure and contents. Look on the top of the anterior end of 

 the pharynx for the brain. Remove the digestive system and, 

 lying below it, look for the nerve chain of ganglia connected to 

 the brain by nerve-threads encircling the pharynx. Make cross- 

 sections of various parts of the body of hardened specimens and 

 examine the structure. 



MoLLDSCA. — The examination of a Snail is not easy, conse- 

 quently the student would best use one of the Lamellibranchs, 

 as the Clam or the Fresh-water Mussel. Put live clams in dishes 

 of sea-water or mussels in fresh-water, the bottoms of the 

 dishes being covered with a layer of sand three or four inches 

 deep. Watch the animal crawl about and finally bury itself in 

 the sand. Note the streams of water entering and leaving the 

 siphons. Touch the tentacles at the margin of the siphons and 

 note their sensitiveness. Of the anatomy, study first the shell 

 — its shape as seen from various directions, the covering or so- 

 called "epidermis," the position of the hinge. Separate the 

 two valves and remove the soft part of the bodj', noting where 

 and how this is attached to the shell, how the valves are held 

 together ; examine the hinge-ligament and hinge-teeth, the mar- 

 gin of the valves, and their thickness in various places. Note 

 the scars left by the adductor muscles and the siphons (Fig. 



