vi NEMATODA STRONGYLIDAE 143 



The genus Stronyylus is easily recognised by its conspicuous 

 genital bursa, strengthened by variously arranged ridges which are 

 of specific value. There are numerous species, found for the most 

 part in mammals, but also in birds and reptiles. Some species 

 inhabit the intestine, others form aneurisms in the large blood- 

 vessels, and cause considerable mortality amongst horses ; others 

 live in the tracheae and lungs of cattle and sheep, their presence 

 often causing great loss to the farmer. No intermediate host has 

 been satisfactorily demonstrated ; the larvae live in damp earth, 

 and it seems almost certain that they pass directly into their 

 host with its food. 



Dochmius (Ancylostomuin) duodenalis, called by Neumann * 

 Uncinaria duodenalis, is one of the most dangerous parasites that 

 attack man. It lives in the duodenum and jejunum, and the 

 fertilised eggs leave the body of its host with the excreta, and in 

 damp earth develop into larvae in the course of a few days. 

 These at first eat voraciously, but after undergoing several moults 

 they cease to take food and pass into the resting stage. If now 

 they are swallowed with drinking water, they come to rest in 

 the small intestine of their host, and in a few weeks become 

 sexually mature. They cause great harm by burrowing in the 

 intestinal walls and destroying the capillaries. They are found 

 by hundreds, and even thousands, in the same host, and pro- 

 duce profound anaemia, which is frequently fatal to miners, 

 and was the cause of a great mortality amongst the workers 

 in the St. Gothard Tunnel some fifteen years ago. This 

 species is very widely spread over the face of the globe. Docli- 

 mius trigonocephala Eud. and D. stenocephala produce similar 

 diseases in dogs and cats, and D. cernua Crep. is found in sheep 

 and goats. 



The genus Cucullanus exists in the adult form in the intestines 

 of fishes, and more rarely of reptiles. C. eleyans Zed., which live 

 in fresh-water fish, e.rj. the perch, is viviparous ; after birth the 

 young pass into the water and make their way into the aliment- 

 ary canal of the small crustacean Cyclops, and thence into its 

 body-cavity. Here they undergo two moults, accompanied by 

 certain changes in structure. If this second host be swallowed 

 by a fish the parasites are set free, and develop generative organs. 



1 A Treatise mi Parasites ami Parasitic Diseases. English Trans, by G. Fleming, 

 London, 1892. 



