MALARIA EXPEDITION TO NIGERIA 5 
Genus Dochmius. Anterior end turned towards dorsum. Mouth oval, 
limited by a chitinous border, followed by a chitinous buccal capsule, the dorsal wall 
of which is shorter than the ventral, and is supported by a conical rib, the point of 
which may project into the cavity. At the bottom of the capsule on the ventral wall 
are two teeth ; towards the free edge the ventral wall also bears two other teeth, which 
are hooked at their extremities. The dorsal free edge is also sometimes similarly 
toothed. There are several species inhabiting the intestinal canal of man (Z). or 
Ankylostoma duodenale), anthropoid apes, dogs, cats, sheep, and goats, wolf, fox, etc. 
Life history : According to Railliet 9 and others, the embryos which hatch out, 
from the already segmented ova a few hours after leaving the intestine, under favour- 
able conditions and after several moults, reach a stage in which they again, on gaining 
access to the alimentary canal, develop into adult ankylostomes. He mentions that 
Leichtenstern has asserted that some larvae become transformed into sexually mature 
rhabditiform adults, which again produce larvae. Giles 10 also reports having traced 
the life history of the parasite through a sexually mature rhabditiform stage, the 
larvae of which become adult ankylostomes in the intestine of man.* 
Genus Sclerostomum. Truncate anterior extremity, straight or slightly curved 
towards the ventral surface. Mouth circular, open, followed by a chitinous buccal 
cavity furnished along its edges with numerous teeth, disposed in one or several 
series. Male has two spicules and a generally tri-lobed caudal bursa. Vulva of 
female opens in posterior part of the body. 
Several species have been found in the intestinal canal of the horse, mule, 
sheep, goat, deer, roe, antelope, etc. 
Life history: Railliet" describes the following in the case of S. equinum: the 
eggs, passed with faeces, develop in water into embryos, which are taken up again 
probably in drinking water. They probably pass from the intestine into the 
circulatory system, and after a sojourn there return to the mucous membrane of 
the caecum, where they remain until a definite stage is reached, whereupon they pass 
into the intestine and pair. Giles, 12 however, in the case of S. tetracanthum, says 
that rhabditiform adults are produced as in the case of Dochmius duodenale. 
Genus Cucullanus. Exists in the adult form in the intestines of fishes and 
reptiles. One species ( C. elegans ) lives in fresh water fish, e.g., perch ; while the 
young inhabit the body cavity of the crustacean Cyclops. 
Genus Syngamus. Head end thickened. Mouth large. Chitinous buccal 
capsule. Males small ; two spicules. Females have double ovary ; vulva situated 
in anterior part of body ; the male is generally permanently attached to the female, 
its genital bursa being closely adherent to the vaginal opening. 
9. Railliet Traite' de Zoologie Mcdicah et Agricole. Paris, 1895. P. 46'. 
10. Giles Report on Kala-azar and Beri-bcri. Shillong, 1890. 
* The recent researches of one of us (Annett) tend to confirm the truth of these investigations. 
II. Railliet, Traite de Zoologie Medicate et Agricole. Paris, 1895. 459- 
12. Giles, Some observations on the Life History of Sclerostomum tetracanthum : Scientific Memoirs by Medical Officers of tin- 
Army of India. Part VII. Calcutta, 1892. 
