CROSSOBOTHRIUM 75 



consisting of a scolex and not more than one or two proglot- 

 tids. Place this on a slide, cover, being careful not to com- 

 press 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 transparent tubes. These are portions of the water vas- 

 cular system. Recall the description of this system given in 

 the lecture or in textbooks. 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 continual 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, threadlike 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 tapeworms 

 have these "motile proglottids," which in some cases remain 

 alive for so long after being detached as to seem almost like 

 independent animals. Ripe proglottids, taken from the in- 

 testinal 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. 



Mount stained specimens of proglottids in balsam and 

 study the reproductive organs. 1 



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

 Enough pressure should be used to flatten the proglottids decidedly. 



