FREE-LIVING NEMATODES 



499 



56 (si) Caudal glands and cephalic setae absent. . . . Alaimus de Man. 



The species of this small genus have a 

 rather simple structure. All are slender. 

 Some appear to be parthenogenetic. 



Representative species. 



Alaimus simplex Cobb 1914. 



c 

 c 



Very minute striations in subcuticula at 

 extremities, under favorable conditions. 

 Obscure traces of lateral wings. Eggs ap- 

 parently deposited before segmentation be- 

 gins. Whether two testes or only one not 

 determined. Broad, rounded, blunt end of 

 testis, located as far behind base of neck as 

 latter is behind anterior extremity. 



Habitat: Big Lake, Fla. 



Fig. 803. Alaimus simplex. 



I, lateral view of a female; II, anterior ex- 

 tremity, lateral view; III, posterior extremity 

 of a male, lateral view. 



a, lip region; b, pharynx; c, amphid; d, 

 amphid, enlarged; e, group of spermatozoa at 

 posterior portion of ovary ;/, blind end of ovary; 

 g, male supplementary papillae; h, left spicu- 

 lum; J, terminus; j, submedian elevation or flap 

 indicating rudimentary bursa; k, egg; /, vulva; 

 m, nerve-rin§; n, posterior extremity of esopha- 

 gus; p, modified cells of anterior intestine; q, 

 cuticula; r, wall; s, lumen of intestine; /, flexure 

 in single ovary. (After Cobb.) 



57 (50) Pharynx present 58 



58 (59) Pharyngeal cavity relatively large, amphids very small if any. 



Prismatolaimus de Man. 



Well-characterized genus consisting at present of four 

 or five species. This genus resembles Monhystera to a 

 certain extent. 



Representative species. 



Prismatolaimus stenurus Cobb 1914. 



c= 



Behind each amphid, at a distance equal to the width 

 of two to three annules of the cuticula, there is a short 

 seta. The ovaries are moved backward and forward 

 in accordance with stage of development of eggs. These 

 latter appear to be deposited before segmentation begins. 

 Notwithstanding the slenderness of the tail caudal glands 

 and a spinneret are present. 



Habitat: Roadside pool, Doxiglas Lake, Michigan. 



Fig. 804. Prismatolaimus stenurus. 



I, lateral view of a female; II, front view of head; III, side 

 view of head. 



a, one of the six cephalic papillae; 6, one of the ten cephalic 

 setae; c, one of the six thin lips; d, pharynx; e, amphid; /, 

 lumen of the esophagus; g, nerve-ring; k, cuticula; i, nucleus 

 of ovum; j, vulva; k, blind end of posterior ovary; /, egg; *«, 

 beginning of the intestine; «, one of the cells of the wall of the 

 jntestioe; o, rectum; p, anus; q, one of the caudal glands; f, 

 flexure in anterior ovary; s, spinneret. (After Cobb.) 



