PARASITOLOGY. 171 
the worm; two are located dorsaily and two ventral- 
iy 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, toa 
certain extent, anindividual 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 
aripe 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. 
