60 ANIMAL LIFE 
case of some of the parasitic worms which live in the bod- 
ies of other animals, the male has an extraordinarily de- 
graded, simple body, much smaller than that of the female 
and differing greatly from that of the female in structure. 
In some cases even—as, for example, 
the worm which causes “ gapes” in 
chickens —the male lives parasiti- 
cally on the female, being attached to 
the body of the female for its whole 
lifetime, and drawing its nourish- 
ment from her blood (Fig. 29). 
A condition known as partheno- 
genesis is found among certain of 
the complex animals. Although the 
species is represented by individu- 
als of both sexes, the female can 
produce young from eggs which 
have not been fertilized. For ex- 
ample, the queen bee lays both fer- 
tilized and unfertilized eggs. From 
the fertilized eggs hatch the work- 
ers, which are rudimentary females, 
and other queens, which are fully- 
oe On thhaleaiy when developed females ; from the unfer- 
yngamus trachealis), which ,_, 
causes the ‘gapes” in fowls, tilized eggs hatch only males—the 
The male is attached to the drones. Many generations of plant 
female, and lives as a para- ,, 
site on her. lice are produced each year parthe- 
nogenetically — that is, by unferti- 
lized females. But there is at least one generation each 
year produced in the normal way from fertilized eggs. 
Some of the complez animals are hermaphroditic—that 
is, a single individual produces both egg cells and sperm 
cells. The tapeworm and many allied worms show this 
condition. This is the normal condition for the simplest 
animals, as we have already learned, but it is an excep- 
tional condition among the complex animals. 
