THE ROUNDWORMS OF DOMESTIC SWINE. 



11 



wide by 83 to 98 p long, is marked on the inside by a series of chitinous ridges in the 

 form of continuous spirals (or a multiple spiral), all running in the same direction and 

 appearing like the threads of a quadruple screw. 



Esophagus 3.1 to 3.7 mm. long, or about one-fourth of the body length, and 117 to 

 127 ft wide at its widest part near the base. Nerve ring 0.35 mm. and excretory pore 

 0.48 mm. from the anterior end. 



Male 10 to 15 mm. long, averages about 13 mm. in length; 301 to 387 p wide at the 

 widest part just above the bursa. The bursal wings extend from a point about 1.2 

 mm. from the caudal extremity to the tip, the body ending in a blunt point. Bursal 

 wings irregularly ovate, ^^^^^^^.^ 



asymmetrical, the right bur- 

 sal wing being about twice 

 as wide as the left wing. 

 The bursa contains 5 pairs 

 of stalked papillae asym- 

 metrically arranged, of 

 which 4 pairs are preanal 

 and the last pair is post- 

 anal. Bursa marked with 

 fine longitudinal striae, in- 

 creasing in density toward 

 its base (fig. 2). Spicules 

 two, grooved on the ven- 

 tral surface, the left spicule 

 2.24 to 2.95 mm. long, 

 very slender, ending in a 

 fine point and presenting 

 a slightly concave sur- 

 face near the tip on the 

 dorsal side. The right 

 spicule (about one-fifth of 

 the length of the left spicule) 

 is stouter and blunter at the 

 point, measuring 10 [i at its Jr / 



base, or nearly twice the jr 10fTim. 



width of the base of the 

 long spicule, and is 457 to 

 619 (i long (fig. 3). Anus 

 155 to 200 ft from the pos- 

 terior end and surrounded 

 on the posterior and left side 

 by a cuticular thickening 

 (circumanal ring), the outer 

 edge of which is serrated. 



Female 16 to 22 mm. long, 

 263 to 420/i wide; average maximum width 368 p, at a point about one-third of the 

 distance from the head to the caudal end. For the next third of the distance the 

 width remains constant except for a slight constriction in the region of the vulva. 

 Beginning at a point about two-thirds of the distance from the head to the caudal 

 end, where one of the uteri turns back on itself, the width gradually diminishes and 

 then abruptly decreases a short distance in front of the anus. Anus 215 to 275 p 

 from the caudal tip (fig. 4). 



The orbicular naked vulva opening near the left side close to the lateral cuticular 

 wing is slightly anterior of the middle of the body, dividing the worm anteriorly and 

 posteriorly in the ratio 5 : 6. Vagina uniform, about 49 p in diameter, 1.7 mm. long, 



FIG. 2. Arducnna strongylina. Bursa of male, ventral view, cl., 

 cloaca; l.b.w., left bursal wing; I. sp., long spicule; po. p., post- 

 anal papillae; pr. p., preanal papillae; r. b. w., right bursal wing; 

 . sp., short spicule; v. r. c., ventral ridge of the cuticle. X75. 

 (Original.) 



