24 
LIFE HISTORY OF AGCHYLOSTOM A DUODENALE OR UNCINARIA 
DUODENALIS. 
The eggs (tig. 16) are laid in the intestinal tract of the patient by 
the female worms and are discharged in the feces, either unsegmented 
or during the early stages of seg- 
mentation. They will not develop 
into adult worms in the intestine, 
but must tirst pass out of the body. 
Thus, for every adult hookworm 
present in the bowels a separate 
germ must enter the body. 
The egg has a thin shell, which is 
an indication of a simple life cycle. 
A short time after escaping in the 
feces — the time varying according 
to temperature, moisture, and posi- 
tion in the feces — each egg devel- 
ops (tigs. 17-27) a minute embryo, 
which is known as a rhabditiform 
embryo (tig. 27). This name is given 
to it because of its resemblance to 
worms of the genus Bhcchditis. Characteristic for this stage is the 
rhabditiform esophagus, which is entirely different from the esophagus 
Fig. 16. — Eggs of Old World hookworms 
{Agchylostoma duodenale) as found in the 
stools. Greatly enlarged. (After Stiles, 
1902b, p. 193, fig. 128.) 
Figs 17-29. — Embryology of the Old World hookworm {Agchylostovia duodenale) of man; 17-23, seg- 
mentation of the egg, 24-26, the embryo; 27, a rhabditiform embryo escaping from its eggshell; 28-29, 
empty eggshells. Greatly enlarged. (After Perroncito, 1882, p. 342, fig. 142.) 
of the adult hookworm. This embryonal esophagus is more or less 
bottle shaped, and consists of three parts — an anterior elongated 
