54 VERMES. 



Class II. Nemathelmia (Nemathelminthes). 

 Round-Worms. 



Body cylindrical, unsegmented, devoid of lateral locomotor append- 

 ages, with papillae or armature of hooks at the anterior end. No blood- 

 vessels nor specialized respiratory organs. Predominantly parasitic. 

 Sexes separate. Development generally without metamorphosis. 



Order 1. Nematoda. Thread- worms. Usually possess a straight ali- 

 mentary canal, and paired excretory tubes contained in lateral lines and 

 opening by a ventral pore behind the terminal mouth. The male with 

 curved tail-end and copulatory spicules, smaller than the female. The 

 young form often inhabits an intermediate host. Ascaris lumbri- 

 coides, round-worm of man (and as a smaller variety in swine) ; the 

 transference probably takes place by an intermediate host (Julus guttu- 

 latus ?). A. mystax, in the cat and dog, occasionally in man . A. mega- 

 locephala, in the horse and ox. Oxyuris vermicularis, thread- worm, 

 in the large intestine of man ; the female ten millimetres long. Stron- 

 gylus. Rhabdonema nigrovenosa, as a viviparous hermaphrodite in 

 the frog's lung, producing a generation with separate sexes (Rhabditis), 

 which becomes sexually mature in damp earth (heteromorphous genera- 

 tion). Dochmius duodenalis, 16 millimetres long ; in the small intes- 

 tine of man, in Europe, Egypt, Comoro Islands, Brazil, and Cayenne. 

 Trichocephalus dispar, whip-worm, in the human colon ; transfer 

 without intermediate host by filthy food. Trichina spiralis, in the 

 intestine of man and other omnivorous mammals. The viviparous 

 female trichina of the intestine, about eight days after its introduction, 

 begins to bear young, which penetrate the wall of the intestine and 

 make their way actively or by means of the blood-stream, into the 

 muscles, here within fourteen days to develop into spiral worms and to 

 encyst ; they first attain sexual maturity in the intestine of some other 

 warm-blooded animal. This form is maintained by means of the house- 

 rat. Filaria (Dracunculus) medinensis, Guinea-worm, in the subcuta- 

 neous connective tissue of man ; the young form in Cyclops. Mermis, 

 devoid of anus, in the body-cavity of insects, thence to damp earth, where 

 sexual maturity is reached. SphSBrularia bombi, in female humble- 

 bees which survive the winter. Gordius aquaticus, in insect larvae, 

 later in the body-cavity of predatory insects ; then becomes mouthless 

 and sexually mature in water. Anguillula aceti, vinegar-eel, free- 

 living. Tylenehus tritici, in wheat, &c., causing ear-cockle; young 

 form in earth. Dorylaimus, common in mud. 



