78 INVERTEBRATE ZOOLOGY. 



animals, generally molluscs, and by a variety of expedients become transferred 

 to their final Vertebrate host. Collect a few of the common brown snails found 

 in ponds, break olf the shell and examine the soft brownish mass which fills the 

 apex of the whorl. This mass is the liver and may be frequently fomid filled 

 with minute worms of different shapes. These may be transferred to a slide 

 with a pipette, mounted in a drop of water, covered and examined. The 

 three main forms are the sporocyst, redia and cercaria, which are very easily 

 distinguished and may be identified by referring to any text book. (Claus or 

 Lang.) Good ijermanent mounts are difficult, but may be done by applying 

 the different reagents drop by drop upon the slide, and removing the liquids 

 as desired, by inclining the slide and using a cloth or piece of blotting paper. 

 The entire process should be performed under a dissecting lens. A quantity 

 of the material may also be prepared at one time by careful decantation 

 [cf. 38], or perhaps an entire snail's liver may be stained and the separate par- 

 asites subsequently dissected out. 



Type VII.— Taenia Crassicollis. 



48. This is the common Tape-worm of the domestic cat, and is found in 

 the adult state in the intestines of that animal. To obtain specimens of this, 

 the intestines of all the cats used in the Vertebrate course are opened with 

 scissors and examined. They are seldom found in kittens, and are found in 

 about one out of three adults, there being often 4-6 entire worms in one host. 



[If convenient, one or two cats will be examined before the class at this 

 point, that the Taeniae may be seen in their environment.] 



49. Superficial examination. Keep the specimen in a glass dissecting 

 pan, covered with TO;;/ and observe : — 



(a) The Scole.v or •' head." This is the blunt point at the anterior end of 

 the animal, and is not in the shape of a rounded knob with attenuated neck, 

 as in most tape-worms, [cf . specimens of T. Saginata, etc. Also notice specific 

 name, CrassicoUiii.] Notice on the Scolex form rounded depressions, the 

 suckers, also a double row of chitinous hooks. Place the specimen for a mo- 

 ment upon a slide and bring the Scolex under 50-60''. Notice the shape and 

 arrangement of the hooks. 



(b) The Proglottids or " links." These resemble the segments of segmented 

 worms, but in reality are not, but are contiinially produced by vegetative 

 growth from near the base of the Scolex. The proglottids at the free (poste- 

 rior) end are the oldest and are sexually mature, while towards the scolex they 



