668 



NEMA THELMINTHES 



head gland, which runs through nearly half the length of the body. 

 In the floor of the mouth there are two ventral chitinous plates, and 

 the prominent opening of the dorsal head gland (often called a tooth). 



Male measures about lo millimetres in length by 0-4 to 0-5 milli- 

 metre in breadth, and possesses a bursa copulatrix at the posterior 

 end, which is umbrella-shaped and supported by 

 chitinous rods, which are arranged as follows: In 

 the median dorsal line is the costa dorsalis, which 

 divides dorsally into two small branches, which 

 are ramified at their tips. Postero-laterally there 

 is one root on each side — the single costa dorsalis 

 externa, in front of which is a single broad lateral 

 root, which divides into the costa lateralis posterior, 

 the costa lateralis media, and the costa lateralis 

 externa; while anteriorly also on each side is the 

 costa ventralis. Through the opening of this bursa 

 project the two spicules, unless they are retracted, 

 which are long and slender, and measure about 2 

 millimetres in length. The male generative appar- 

 atus consists of a testis in the form of a tube, an 

 oval vesicula seminalis, and a long cement gland, 

 whose secretion fixes the male to the female during 

 conjugation, and a spicule sac. 



The female measures 12 to 13 millimetres in length, 

 and has the vulva at the junction of the middle 

 and hinder parts of the body, from which a short 

 vagina opens into two tubes, which are divisible into 

 ovijector, uterus, receptaculum seminis, and an 

 ovary. 



Life-History. — The adult worms live chiefly in the 

 jejunum of the host, where 

 they feed upon the villi. 

 Blood is only accidentally 

 found in a worm. Here 

 the females lay the eggs, 

 which are oval in form, 

 with broad rounded poles, 

 surrounded by a colourless 

 shell, which is really 

 double, but looks single, 

 inside which lies an oval 

 granular mass separated 

 from the shell by a con- 

 siderable space. As the 

 egg travels down the alimentary canal the granular mass divides 

 into two, and finally into four segments, in which condition the 

 egg is usually found in the faeces. Development proceeds in the 

 faeces, depending upon the temperature of the atmospheric air. In 

 twenty-four hours, if supplied with air water, and heat, the embryo 



Fig. 291. — An- 

 cylostoma duo- 

 denale Dubini: 

 Male. 



(After Looss.) 



Fig. 292. — Anterior End 



OF Ancylostoma duoden- 

 ale Dubini. 



(After Looss, from Mense's 

 ' Tropenkrankheiten.') 



