A TAPEWORM (Tsniasp.). 



Phylum IV, PLATYHELMINTHES; class 3, CESTODA; order 2, POLYZOA. 



HABITAT. This class of flat worms is entirely parasitic, living as 

 an adult in the intestinal tract of various vertebrate animals. The 

 cestodes have also an intermediate host in which they pass the larval 

 state encysted in various tissues, as muscles, liver, brain, and peri- 

 toneum. 



Technical Note. Tapeworms of the genus T&nia can be obtained for 

 class study from the intestines of the dog or cat. Slit open the in- 

 testine, rinse with tepid water and remove the slender, ribbon-like 

 worms a few inches in length which will be found attached by one end 

 to the walls of the tract. If they are to be studied at once they may be 

 kept alive for some time in a dish of blood-warm normal salt solution. 

 If they are to be preserved use two per cent formalin or seventy per 

 cent alcohol. For examination and study place in a shallow dish of 

 water the salt solution if the animal is alive. 



STRUCTURAL FEATURES. Note the following details, verifying all 

 statements herein made: 



a) The body, made up of a great many proglottids or false segments. 



As we shall see later, these are entirely different from the somites or 

 real segments of the earthworm and the arthropods. 



b) At the smaller end of the string of proglottids is a terminal knob, the 



scolex. This is the head of the animal. It is attached to the 

 inner wall of the host's intestine by several suckers and also 

 usually by two rows of chitinous hooks. Determine the number 

 of these suckers and note presence or absence of the hooks. 

 Where are the largest and where the smallest proglottids ? The 

 youngest ? The oldest ? Understand where and how the pro- 

 glottids originate in development. 



Exercise i. Count the number of proglottids and draw the animal on a 

 scale enlarged sufficiently to show detail. 

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