PARASITOLOGY. 171 



the worm: two are located dorsally and two ventral- 

 ly and open at the posterior border of the last seg 

 ment through an opening called the caudal foramen. 

 The segments develop from the neck ; each new seg- 

 ment pushes the preceding one on. until there is a 

 chain of segments. As the segments grow they be- 

 come longer and wider so that the strobilus 

 (strobilos — pine cone, meaning adult tapeworm) 

 has an attenuated appearance anteriorly with a narrow 

 neck and a very small head. Each segment is, to a 

 certain extent, an individual within itself. It absorbs 

 nutrients and through its integument exchanges 

 gases. It is a hermaphrodite, possessing both male 

 and female genital organs. The genital pore is 

 located on the side of each segment. In some spec- 

 ies there is a genital pore on each side, the segment 

 being a double hermaphrodite. The sexually devel- 

 oped segment is called a mature segment; the seg- 

 ment whose uterus is filled with mature ova is called 

 a ripe segment and is ready to detach itself and 

 produce its kind. The tapeworms of the horse, ox 

 and sheep are all unarmed. The life cycle is un- 

 known ; most of the adult tapeworms of man, dog 

 and cat are armed, and the life cycle known. In this 

 life cycle the larval stage is developed in another 

 animal ; this stage is called the cystic or hydatic 

 stage. 



The condition of an animal harboring tapeworms 

 is called taeniasis. 



TAENIDAE. 



The family Taenidae belongs to the order Cestoda 

 under which the genus Taenia is placed. 



