26 
ures 0.3 mm. in length; the anterior end is blunt, the tail long and 
pointed; 6 points ar® visible around the mouth, and these develop 
later into the papillse; the buccal cavity is 10 pi long, 1 A pi in diameter, 
and possesses a highly refractive chitinous membrane; the anus is 50 pi 
from the tip of the tail; excretory pore 50 pi from anterior end; 160 
yw from anterior end is seen the primordium of the genital system. 
In this stage the embiyo takes food and grows. About the second 
Fig. 32. — A young' hookworm {Agchylostoma duodenale) of man, without buccal capsule, four days 
after infection: a, anus; c. g., cervical gland; g, primordium of genital organs; n. s., nervous sys- 
tem; p., papillae on head; p. e., excretory pore; p. in. c., primary mouth cavitj". X about 190 times. 
(After L 00 .SS, 1897, p. 919, fig. 1.) 
Fig. 33. — Anterior end of a young hookworm {Agchylostoma duodenale) during formation of pro- 
visional buccal capsule: c. g., cervical gland; e. g. d., dorsal esophageal gland; e. g. v., ventral 
esophageal gland; n. ni., new mouth; p., papillae on head; p. e., excretory pore; p. vi. c., primary 
mouth cavity. X 578. (After Looss, 1897, p. 920, fig 2.) 
Fig. 34. — Head of larval hookworm {Agchylostoma duodenale) before entering fourth stage, five or six 
days after infection; n. in., new mouth; p. c. in., primary mouth cavity, which extends through 
the provisional buccal capsule and continues as lumen of the esophagus. X 578. (After Looss, 1897, 
p. 921, fig. 3.) 
or third day the embryo casts its first skin, but does not change its 
organization. After about four or five daj^^s (at 27° C.) it measures 
480 pi long by 30 pi in diameter. 
Second stage . — After the fifth day the young worms begin to show 
signs of a second eedysis, at the same time undergoing certain othei 
changes. Three minute lips, each with two very delicate papillae, 
appear under the skin at the anterior end; the brightly refringent cutic- 
