FREE-LIVING NEMATODES 



48s 



II (12) Pharynx simple, male supplementary organs not in fascicles. 



Dorylaimus Dujardin. 



Genus consisting, no doubt, of hundreds 

 of species, and inhabiting soil, fresh water^ 

 and, to a limited extent, brackish water. 

 They feed so far as known on vegetable 

 matter, most commonly, it is believed, on 

 the roots of plants which they pierce by 

 means of the hollow oral spear. 



Representative species. 



Dorylaimus fecundus Cobb 1914. 



i- 



Habitat: Algae, Potomac River, Wash- 

 ington, D. C. 



Fig. 779. Dorylaimus fecundus. 

 At the right, head and tail of a female; at the left, 

 tail end of a male, 

 a, apex of spear, showing oblique opening; 

 b, papilla of the anterior circlet: c, papilla of 

 the posterior circlet; d, guiding-ring for the 

 spear; e, commencement of the esophagus, 

 /, pre-rectum; g, rectum; h, anus; i, anal 

 muscles; j, caudal papilla; k, outer cuticula; 

 /, inner cuticula; m, muscular layer; », pre- 

 rectum; o, one of the numerous oblique copu- 

 latory muscles; p, one of the ventral series of 

 male supplementary organs; q, ejaculatory duct; r, pair of pre-anal papillae; s, retractor muscles of the 

 spicula; /, muscular layer; m, right spiculum; t, accessory piece. (After Cobb.) 



12 (11) Pharynx with complicated radiate framework, male supplementary 

 organs in fascicles Actinolaimus Cobb. 



Genus represented in all parts of th world, and proposed for 

 species similar to Dorylaimus labyrinthostonius, in which the 

 pharynx is more or less immobile, radially striated and elabo- 

 rately constructed. 



Representative species. 



Actinolaimus radiatus Cobb 1913. 



e. .3 6 4 [9 •» «. , .- ^ 



9 ] 5 17 2 i~4~ '™*" 



The esophagus begins 



Cr ■' "■ "■ -"- "' < 1 m, as a tube about one- 

 ^" '■ '<■ '■ '■""'* ■ third as wide as the cor- 



responding portion of the neck. It continues to have this width 

 for some distance. Considerably in front of the middle of the 

 neck it expands rather suddenly. The cells of the brownish intes- 

 tine contain granules of variable size, arranged so as to give rise 

 to a rather obscure tessellation. The tail of the female is concave- 

 conoid to the hairfine terminus. The tail of the male is hemi- 

 spherical-conoid. Immediately in front of the anus are two ven- 

 tral papillae placed side by side. In addition to these there are 

 ventral papillae arranged in three raised and conspicuous groups 

 or fascicles. These three groups form a series whose length is 

 about equal to the distance from the posterior group to the end 

 of the tail. The two equal, sUghtly arcuate, rather acute 

 spicula are about twice as long as the anal body diameter. The 

 surface of the tail carries a number of innervated papillae, at 

 least as many as six, and probably quite a number of others. 



Habitat: Roots of plants and among algae, Potomac River and 

 its banks, Arlington Farm near Washington, D.C.; Douglas 

 Lake, Mich. 



Fig. 780. Actinolaimus radiatus. 



lb, lip region; pp, innervated papillae; pk, pharynx; on, onchus or 

 spear; or, mouth opening. (After Cobb.) 



Oral end without protrusile spear or sting 14 



Pharynx armed with one or more refractive, cuticular teeth. . . 15 



x-S/4 



13 (2) 



14 (37) 



