CROSSOBOTHRIUM LACINIATUM. 55 



5. Cut from the head-end of a Hving specimen a piece con- 

 sisting of a scolex and not more than one or two proglottids. 

 Place this on a shde, cover, being careful not to compress too 

 much at first, and examine the scolex carefully again to make 

 sure you understand its structure. 



6. Look for transparent tubes coiling about in the scolex 

 and its suckers. Compress the specimen by drawing off as much 

 water as possible with filter-paper, and look again for the trans- 

 parent tubes. These are portions of the water-vascular system. 

 Recall the description of this system given in the lecture or in 

 text-books. The finer branches which lead from the main trunks 

 are difficult to identify with certainty, but by using the high power 

 of your microscope, and focusing just below the surface in the 

 more transparent portions of the scolex, the flame cells may easily 

 be seen. The " flame " appears like a short, thick whip lost in con- 

 tinual vibration. Find such flames and watch them carefully. If 

 not found at once, let the preparation stand and examine in about 

 half an hour. In the older preparation they are frequently easier 

 to find. 



7. In both scolex and proglottids of fresh specimens many 

 clear, transparent, thread-like muscle fibers may be seen. There 

 will also be found an abundance of clear, rounded granules of 

 lime. 



8. Watch the movements of the large, detached proglottids. 

 Pull proglottids from the posterior end of the specimen to see how 

 easily they may be detached. Very many tape-worms have these 

 "motile proglottids," which in some cases remain alive for so long 

 after being detached as to seem almost like independent animals. 

 Pipe proglottids, taken from the intestinal fluid of the host and 

 placed in sea-water, begin within a few minutes to extrude eggs. 

 Extrusion is accompanied by peculiar and extensive muscular 

 contractions. 



if 



Mount stained specimens of proglottids in balsam and study 

 the reproductive organs.^ 



1 Specimens may be killed in the manner described for Bdelloura. 

 Enough pressure should be used to flatten the proglottids decidedly. 



