FREE-LIVING NEMATODES 



487 



19 (18) Main tooth submedian. Lips thin; setae present 20 



20(21) Males without bursa Oncholaimus Dujardin. 



Genus of numerous species, nearly all 

 marine. A few species only in brackish 

 and fresh water. Cosmopolitan, extend- 

 ing well into the polar seas. Some attain 

 a length of 25 to 30 mm. The individuals 

 sometimes occur in enormous numbers. 



/ /filK/JIf.-! The pharyngeal teeth vary in number, 



form, and size, and afford good specific 

 characters. The segments of the esopha- 

 gus frequently contain much-branched 

 "salivary" glands emptying through the 

 pharyngeal teeth. 



The female sometimes possesses a pecu- 

 liar pair of relatively large organs of un- 

 known significance emptying through 

 pores toward the tail end. 



Representative species. 

 Oncholaimus punctatus Cobb 1914. 



X897 



FIG. 783. Oncholaimus 

 punctatus. 



a, thin flaps on margins 

 of lips; b, lips; c, anterior 

 circlet of papillae; d, poste- 

 rior circlet of papilla-like 

 cephalic setae; e,J, subme- 

 dian tooth or onchus; g, wall 

 of pharynx; h, intestine; i, 

 ejaculatory duct; j, spic- 

 ulum; k, dorsal tooth or 

 onchus; /, amphid; m, am- 

 pulla of gland, emptying 

 through dorsal onchus, k; 

 n, rectum; o, beginning of 

 esophagus ; p, anus ; q, lin- 

 ing of esophagus; r, caudal 

 gland; 5, caudal papilla; 

 /, ducts of the three caudal 

 glands ; u, spinneret. (After 

 Cobb.) 



21 (20) Males with bursa. 



Oncholaimellus de Man. 



Much like Oncholaimus, but males have narrow 



bursa. Spicula unequal, or equal. Two species 



known; the type 0. calvadosicus de Man is marine. 



Representative species. 



Oncholaimellus heterurus Cobb 1914. 



1.9 



C \.2/ 22 2.8 2.5 ^1.8 ' 



It is rather difficult to observe the finer 

 details of the cuticula on account of the 

 presence in it of numerous dot-like ele- 

 ments, which are arranged in longitudinal 

 groups, of which the widest are the lateral 

 groups. The longitudinal arrangement of 

 the granules is continuous throughout the 

 body, but it is most marked on the lateral 

 fields. There are six lips. 



Habitat: Fresh- water ponds, Cape 

 Breton Island, Dominion of Canada. 



X457 



?= 



18. 



There are six lips, each bearing on its anterior sur- 

 face, near the margin of the head, a somewhat out- 

 ward pointing, minute, innervated papilla. The cells 

 composing the intestine contain scattered granules, 

 which give rise to a very obscure tessellation, and also 

 certain doubly refractive granules. The posterior 

 testis is the smaller. This is a doubtful Oncholaimel- 

 lus, since there are no pharyngeal teeth, and the 

 amphid varies from that of the type species, as do 

 the spicula, which in the type species are unequal. 



Habitat: Fresh-water pond near Ocala, Fla. 



FIG. 784. Oncholaimellus heterurus. 

 I, side view of head; II, ventral view of head; III, side 

 view of tail end of male; IV, ventral view of anal region of 

 male, a, excretory pore; b, submedian cephalic seta; c, 

 pharynx; d, left flap of bursa; e, esophagus; /, left spiculum; 

 g, accessory piece; h, amphid; i, male post-anal seta and pa- 

 pilla; j, lateral seta; k, spinneret; /, thin lips. (After Cobb.) 



