NO. 2131. NEMATODE PARASITES OF RODENTS— HALL. 193 



GONGYLONEMA NEOPLASTICUM (Fibiger and Ditlevsen, 1914) Ransom and Hall, 1916. 



Synonyms. — Bpiro'ptera species Fibiger, 1913 ; S)inifo'pteTa neoplas- 

 tica Fibiger and Ditlevsen, 1914; Spiroptera {GongyloQiema) neo- 

 plastica Fibiger and Ditlevsen, 1914. 



Specif G diagnosis. — Gongylon&ma (p. 101) : The anterior extremity 

 of the body terminates in a blunt cone, the taper beginning at the 

 excretory pore. The cuticle is finely striated transversely at inter- 

 vals of 6 to 12 If.. Anteriorly, in the vicinity of the proximal portion 

 of the esophagus, the annuiations disappear and are replaced by 

 large vesicular bosses, more or less globular, egg-shaped or sausage- 

 shaped, of very variable size. Mouth has the shape of an equilateral 

 triangle, but is without lips. Papillae inconspicuous. No cervical 

 papillae observed. I^ateral bands distinct, of almost uniform thick- 

 ness, diminishing in size anteriorly and disappearing posteriorly in 

 the anal region. The excretory pore is in the median line on the 

 ventral surface, halfway between the nerve ring and the union of the 

 two halves of the esophagus. Posterior of the mouth is a short 

 pharynx with a thin chitinous lining. The esophagus is in two 

 parts. The anterior portion is short and slender and passes abruptly 

 into the posterior portion, which is much longer and thicker. This 

 portion is about twice as thick as the anterior portion and is of 

 fairly uniform diameter, onh^ increasing slightly in the most poste- 

 rior portion. In optical section the nerve ring shows a granular 

 central portion surrounded by a homogenous coat and with spurs 

 of sarcoplasma extending from the body musculature to the nerve 

 ring. The esophagus is separated from the chyle intestine by a con- 

 striction, but the chitinous lining is traceable somev/hat farther down 

 the intestine. As far dovrn as this lining extends, the intestine sliows 

 faint transverse striations, possibly due to muscular tissue. Poste- 

 rior of this are intestinal valves, sometimes showing arrangement 

 in two rows. The ch^yle intestine is about as thick as the anterioi- por- 

 tion of the esophagus. The rectum is narrower. The anal muscula- 

 ture is well developed. 



Male 15 to 20 nun. long and 110 to 130 /x thick. Cuticle 6 /x thick. 

 The esophagus is one-fourth of the entire length. The nerve ring is 

 45 [h in diameter in a male 15 mm. long. The tail is spirally twisted. 

 The average sized bursa is 462 yu, long with a maximum width of 170 jw. 

 The bursa (fig. 252) is asymmetrical, one side being a third shorter 

 than the other and is elongate oval with a distinct constriction in the 

 middle, more pronounced on the longer side and placed more poste- 

 riorly on the shorter side. The lower convexity is more distinct on 

 the shorter side. The bursa narrows rapidly toward the tip of the 

 10600°— rroc.N.ai.vol.50—lG 13 



