158 ANARTHROPODA 



the internal organs, this space being filled up with a kind 

 of connective tissue called parenchyma. 



Tapeworms. These are so named because they resem- 

 ble a piece of tape. All are parasites and dwell within 



FIG. 184. Human tapeworm fourteen feet in length; h t head. Photograph three 

 fourths natural size. 



various species of vertebrates from fish to man. The 

 life history of Tcenia saginata, a human parasite, is typical 

 of the group. In the adult state it dwells only in the 

 intestine of man and is usually from ten to fifty feet in 

 length. Its head known as the scolex is armed with four 



