3428 



THE WORM- LIKE ANIMALS 



OF Gordius a. showing proboscis, and b. circlets of hooks on the 

 head ; c. two examples lodged in the foot of the larva of a May fly. 



ever, develop no further until introduced into the intestine of a suitable host. For 

 instance, if the muscles of a pig be infested with trichinas, and eaten in an un- 

 cooked state by a human being, the immature worms are set free in the intestine of 

 the new host, where they grow to maturity, and produce young. To the genus 

 Filaria belong two other worms parasitic upon man, and the cause of sickness. 



One commonly known as the 

 guinea worm, and occurring 

 in the tropical and subtrop- 

 ical countries of the Old 

 World, lodges itself beneath 

 the skin, producing abscesses. 

 It may attain a length of 

 several feet, and the opera- 

 tion of extracting it from the 

 patient demands consider- 

 able skill and patience. The 

 second species lives in the 

 blood and lymphatic vessels, 

 and is said to cause elephan- 

 tiasis. The larvae are sucked 



from human blood by mosquitoes. When the insects perish, the worms make 

 their escape into water, where they attain maturity and produce their young, which 

 are subsequently taken into the human body when the water is drunk. 



The family of hair worms, Gordiidce, owe their English name to the resemblance 

 that their long, black, slender, flexible body bears to a hair from a horse's mane or 

 tail, and their scientific title, Gordius, to the peculiar 

 habit the animals have of tangling and entwining 

 themselves in a way that may be compared to a 

 Gordian knot. The best-known species is G. 

 aquaticus, the average length of which is about 

 four inches, although specimens three times that 

 length have been obtained. The width of a male 

 is about one-thirtieth of an inch, the females being 

 slightly wider. The prevailing color is brown of 

 various shades; the males, however, are always 

 darker and more polished than the females, and are 

 often of a deep shining black, while the females vary 



from light yellow to deep yellow brown. Upon the middle of the abdomen, both in 

 males and females, runs a long dark streak, visible even in the darkest males. An- 

 other mark by which the male may be recognized is the bifurcated tail end. 

 Although living a free life in the adult condition, these worms spend the greater 

 part of their lives, up to the last period, in certain insects. The young hair 

 worms, as they issue from the egg, are scarcely more than one twenty-fifth of an 

 inch in length, and most curiously shaped; the body being cylindrical, and consist- 

 ing of a thick fore part, and a thinner tail-like appendage. Out of the front end 



EGGS AND LARVA OF Mermis. 

 (Enlarged.) 



