Morph. E:l 



Nematode gonads are of tubular shape, varying greatly in length, and 

 may be straight, sinuous, reflexed, or coiled back and forth (Plate IV). 

 The male gonad consists of a single testis or paired testes. A single 

 testis is usually present, and this extends anteriorly (Plate IV, Fig. 

 1, A) . However, two testes occur in many nematodes, and these are 

 oppositely oriented, except in Heloidogyne , where they are parallel. 

 The terms diorchic and monorchic are convenient for referring to the 

 two-testes or one-testis condition, respectively. VJhen two testes are 

 present, one usually extends forward and the other backward in the 

 body cavity, but tliey join medially into the vas deferens, which runs 

 posteriorly ventral to the intestine and finally narrows down to an 

 ejaculatory duct which opens into the rectum to form a cloaca (Plate 

 IV, Fig. 1, C). 



Male nematodes, with few exceptions (example, Trichinella ), are pro- 

 vided with copulatory spicules lodged in and secreted by spicule pouches 

 (Plate IV, Fig. 1, D). Often the spicules are accompanied by an acces- 

 sory piece, the gubernaculum (Plate IV, Pig. 1, E), which is a sclero- 

 tization of the dorsal wall of the spicule pouch. 



The female reproductive system, may be paired (Plate IV, Fig. 3, U, and 

 S) or single (Plate IV, Fig. 2), the organ lying in the body cavity 

 along-side the intestine being either outstretched (Plate IV, Fig, 2, 

 3) or reflexed (Plate IV, Fig. h, 5). The terms monodelphic and didel - 

 phic are convenient for indicating the single or double condition of 

 the female tract, respectively. Each gonad consists essentially of an 

 ovary, containing developing eggs, and a tubular portion which, in many 

 forms, is dividiV)le into an oviduct and a uterus. The uterus joins on to 

 the vagina vrhich opens on the ventral body surface at the vulva. Varia- 

 tions of the female reproductive system are shown in Plate IV. 



>Jervous System 



The most easily recognizable part of the nervous system is the nerve 

 ring which encircles the isthmus region of the esophagus (Plate III). 

 Associated with it are a number of ganglia, and, according to CJiitwood 

 and Chitwood (1937), there are six nerves which are directed anteriad 

 from the nerve ring. The four submedial have three chief distal branches. 

 The two lateral have only two branches. These branches innervate sen- 

 sory organs of the anterior extremity (sensory papillae or setae). The 

 amphids are innervated from the amphidial nerves which originate In the 

 lateral ganglia of the nerve ring. Thare are a dorsal, a ventral, four 

 submedian, and one, two or three pairs of lateral nerves situated in 

 the chords of the hypodermis, which proceed posteriorly from the nerve 

 ring. The paired postanal lateral sensory organs (phasmids), the ven- 

 tral supplementary organs of n\ales, and the genital papillae are all 

 innervated by branches from one or the other of the main nerves. The 

 nerves themselves and their branches cannot be seen xjithout special 

 methods for demonstrating thorn or by means of sections. In roiitine 

 microscopic examinations, the only part of the nervous system observed 



