1 86' Introduction to A7iimal Morphology, 



This includes two families : — i. Strongylidse — cylindrical^ 

 long, with a disc or vesicle at the tip of the tail, from which 

 the penis arises ; some have a terminal mouth with six 

 (Deletrocephalus) or 4-8 converging, chitinous rods (Diapha- 

 nocephalus) ; others have a chitinous ring around the head, 

 and a mouth inferior (Dochmius, D. duodenale, of the human 

 duodenum, is common in Egypt) or terminal, and the penis 

 surrounded by three papillse (Stephanurus), or with a two- 

 leaved penis sheath (Sclerostomum). The young of S. ten- 

 tracanthum has a free Rhabditis form. Metastrongylus 

 longevaginatus, with a bilobed male disc and two long yellow 

 spicules, has been found in the bronchial glands of Man. 

 Ollulanus is found in the stomach of cats. Eustrongylus in 

 the human kidney. 2. Trichotrachelidae — body long, with a 

 thread-like neck ; the spiral males have a simple spiculum, 

 sometimes with no penis sheath (Trichina). This form lives 

 encysted and sexless in the muscles of Man, swine, &c. ; but 

 when set free by being swallowed, the sexual organs develop^ 

 young are produced, which burrow and become encysted in 

 the muscles ; the males have two terminal tubercles, one anal 

 and one genital. Onchocerca reticulata, of the muscles of 

 horses, is closely allied. Trichosomum has a tubular penis 

 sheath, and a short neck. In T. crassicauda, of the rat's 

 bladder, there are pigmy males without spicula in the uterus 

 of the females, as well as free living males with spicula. 

 Trichocephalus, the common hair worm of the human 

 caecum, has a long, thread-like neck, a swollen body, and a 

 vesicular, echinulated penis sheath ; its muscle layers are 

 rudimental. 



