heterodera radicicola. 405 



Structure of the Male Worm. 



The mature worm (Fig. 19) is thread-like in appearance and 

 barely visible to the unaided eye, the length varying from 690(x 

 to 2,590/x, with an average of 1,640/x (1.64 mm.). The thickness 

 of the worm is fairly uniform, the average breadth being about. 

 30/x. The extreme breadth of the largest specimen met with was 

 55/x. The anterior end is bluntly rounded, and the posterior 

 end tapers slightly. There is no marked bursa copulatrix or 

 genital wings. The cuticle is quite transparent and is traversed 

 by transverse striations about 3/j, apart. These striae are very 

 prominent in the worm while still encased in the larval cuticle 

 and can also be plainly seen when the worm is viewed en profile. 



Anteriorly there is a definite lip region, consisting of what 

 look to be six radiating papillae marked off from the main body 

 by a slight but distinct constriction. The spear is about 23/a 

 to 26/x in length, the anterior half tapering to a fine point. The 

 three terminal knobs on the spear are very distinct. The spear 

 occupies the entire buccal cavity, and is directly continuous with 

 the lumen of the oesophagus. 



The oesophagus is a fine, relatively straight tube, about lOOp, 

 in length. Its walls are overlain by protoplasmic granules, and 

 the cellular structure of the muscle is not discernible. At the 

 termination of the oesophagus is a thick walled oesophageal (car- 

 diac) bulb with a spherical lumen that, by alternately expanding 

 and contracting, acts as a suction organ in connection with the 

 spear. 



The intestine occupies the posterior two-thirds of the body 

 and has inconspicuous walls. The lumen of the intestine is 

 relatively wide, and is more or less densely packed with proto- 

 plasmic food graules. The intestine opens to the exterior together 

 with the aperture of the vas deferens in a common cloaca situated 

 on the ventral surface about 20fi from the posterior extremity 

 of the body. 



The reproductive organs consist of two testes which extend 

 through the body for a distance of 350/x. Usually the testes lie 

 so close together and are so much obscured by the intestine that 

 they are indistinguishable, but their double character, which is 

 the subject of so much difference of opinion, can be more satis- 

 factorily established when, as in the case of the specimen drawn 

 in Fig. 19, the two testes are asymmetricallv twisted so that their 

 extremities become individually visible. As far as can be observed 

 the testes appear to become contiguous and to coalesce posteriorly 

 so as to produce a single vas deferens. Anteriorly the testes are 

 composed of undifferentiated sex cells, but the posterior vas 

 deferens contains full matured sperm. 



The spermatozoa are irregular amoeboid masses of protoplasm, 

 not provided with a flagellum. 



Connected with the vas deferens are two slightly curved 

 copulatory spicules. They can be protruded to some extent 

 through the cloaca and are chitinous in nature. They measure 

 34/x to 39/x and have boss-like thickenings at their extremity for 

 attachment. 



