490 



FRESH-WATER BIOLOGY 



29(28) Pharynx less conspicuously ribbed; cardiac bulb distinct. ... 30 



30 (ss) Dorsal tooth well developed 31 



31 (34) Pharynx cyathiform then conoid, joining esophagus indefinitely. 32 



Amphids spiral, inconspicuous slits or none. . Chromadora Bastian. 



Genus, aquatic, mostly marine but abundant in fresb waters. 

 Twenty to thirty species known. Found in American fresh waters, 

 no species yet described. Species highly developed, usually of small 

 size. Many possess eye-spots near the head. The males usually 

 have a number of pairs of special unicellular glands emptying through 

 slender ducts into the cloaca. These glands are usually arranged in 

 series of pairs toward the dorsal side of the body some distance in 

 front of the spicula. Amphids, fairly well developed, usually difficult 

 to see because of their peculiar form and position; far toward front 

 of head, usually seen more or less in profile. Cardiac bulb relatively 

 shorter than in Spilophora, and not so distinctly subdivided. Males 

 usually have well-developed series of ventral supplementary organs; 

 such organs are less common and less well developed on males of Spilo- 

 phora. Lateral elements of the transverse striae sometimes modified, 

 but rarely reaching degree of differentiation shown in SpUophora. 



Representative species. . Chromadora minor Cobb 1893. 



°™' Habitat: Pacific Ocean, 



y- ^i 6 3 _ ,4. _M 89. ., . ,, California, and Austraha. 



<^ \.y ' ' 'lii'-' ■ ij 3*8 ■ /fNz.'?' '' 



Fig. 788. Chromadora minor. 

 I, male of Chromadora minor; II, one of the ventral accessory organs of the 

 same nematode; III and IV, head and anal region of the same nematode. 

 a, pharynx; b, eye-spots; c, esophagus; rf, h, ventral supplementary organ; 

 e, nerve-ring; /, excretory pore; g, gland of supplementary organ; i, renette 

 cell; j, organ of unknown nature, accessory to the renette cell; k, blind end 

 of testicle; I, cephalic seta; m, ribs of pharyngeal opening; n, papilla; 

 tf,dorsal tooth; p, pharynx; ^,one of the striae of the cuticula; r, subcephalic 

 seta; y, dorsal eye-spot; (.intestine; M.one of the ventral male supplementary 

 organs; v, ejaculatory duct; w, one of the supplementary organs; x, anus; 

 y, left spiculum; z, accessory piece. 



Achromadora Cobb. 



33 (32) Amphids spiral, well developed. 



Genus proposed for the reception of Chrom~ 

 adora minima Cobb and similar soil and fresh- 

 water species. Distinguished from Chromadora 

 by the presence of well-developed spiral am- 

 phids. The dorsal tooth is farther back and 

 is opposed by a small ventral "pocket" as 

 shown in the figure of Achromadora minima. 

 Species found, probably, in all parts of the 

 world. Known from Australia, Fiji, and 

 various parts of United States and Europe. 



Representative species. 



Achromadora minima (Cobb) 1914. 



f>-- 



Male unknown. Habitat: Soil, El Paso, 

 Texas. Potomac River, Washington, D. C. 

 Fig. 789. Achromadora minima. 



I, lateral view of a female; II, lateral view, 

 cuticular markings; III, lateral view of head. 



a, cephalic papilla; b, cephalic seta; c, one of 

 the ribs of the pharynx; d, dorsal pharyngeal 

 tooth; e, subventral (?) pharyngeal tooth; f, 

 pharynx; g, cuticular markings; h, amphid; *, 

 nerve cell; j, nerve-ring; k, spinneret; I, excretory 

 pore ; m, flexure of ovary ; n, one of the caudal glands; 

 o, blind end of posterior ovary; p, anus; q, intestine; 

 r, vulva; s, one of the granules of the intestine; U 

 egg. (After Cobb.) 



