212 APPENDIX. 



which should be changed several times, until the paper is voided 

 perfectly clean. The worms are then preserved in the ordinary 

 way, and when properly hardened are cut into short pieces, 

 stained with borax-carmine, imbedded in paraffin, and cut into 

 sections with the microtome. 



The living worms should first be observed — their shaj)e, 

 movements, behavior to stimuli, pulsation of the dorsal vessel 

 (time the pulse and vary the rate by temperature changes). 

 "Well-preserved specimens should then be carefully studied for 

 the external characters (draw through tlie fingers to feel the setse). 

 (Sketch.) Observe openings. The nephridial openings cannot be 

 seen, but if preserved worms be soaked some hours in water and 

 the cuticle peeled off tliey may be clearly seen in this. A 

 general dissection of a fresh specimen should now be made, 

 and the positions of the larger organs studied. (Make partial 

 sketch, to be filled out afterwards, as in Fig. 24.) The alimentary 

 canal and circulatory organs should now be carefully studied. 

 Even the smallest of the blood-vessels may easily be worked out 

 under the lens by using fresh specimens (killed in 70^ alcohol 

 and afterwards dissected under water) and carefully turning aside 

 the alimentary canal. 



The alimentary canal should afterwards be cut through be- 

 hind the gizzard and gradually dissected away in front, exposing 

 the nerve-cord and the reproductive organs (wash away dirt with 

 a pipette). ISo great difficulty should be found in making out any 

 of the parts, excepting the testes. These are difficult to find in 

 mature worms, but may be found with ease in those which have 

 no median seminal vesicles (usually the case with specimens hav- 

 ing no clitellum). 



The contents of the seminal receptacles and vesicles from a 

 fresh worm should be examined with the microscope. Kemove 

 an ovary (with forceps and small curved scissors), mount in water, 

 and study. (Stained in alum-carmine and mounted in balsam 

 the ovary is a beautiful object.) The student should also re- 

 move a fresh nephridial funnel and jDart of a nephridium, and 

 study with the microscope. (This may have to be shown by the 

 demonstrator, but should never be omitted, as the ciliary action 

 is one of the most striking things to see.) A careful dissection 

 of the anterior part of the nervous system should also be made. 



