488 



FRESH-WATER BIOLOGY 



22 (17) Teeth small, often only one, then dorsal; lips with inconspicuous 



papillae; pharynx of moderate size 23 



23 (36) Esophagus with one or two bulbs 24 



24 (25) Bulbs two, spinneret absent Diplogaster M. Schultze. 



Genus with more than a score of 

 known species, mostly found in fresh 

 water but also in many moist situations 

 in soil and between the sheaths of 

 grasses, etc. Some species hermaphro- 

 ditic. A number of the species appear to 

 be at least facultative parasites. They 

 are often found in dead insects and cater- 

 pillars; whose death they apparently 

 have caused. Other species are found 

 in decaying mushrooms, animal excreta 

 and foul pools. Many of the species are 

 easily reared in decayed meat and va- 

 rious other cultiure media. Many thrive 

 best in the presence of bacteria. 



Representative species. 

 Diplogaster fictor Bastian 1865. 



I 5 tQm^ 



Striae resolvable near the head into 

 rows of refractive dots arranged in lon- 

 gitudinal as well as transverse lines. A 

 short distance behind the head the longi- 

 tudinal rows arrange themselves in pairs. 

 These pairs indicate the locus of about 

 twenty-four longitudinal cuticular ribs 

 or wings, which extend from the middle 

 of the neck to near the anus. On the 

 tail these ribs again resolve themselves 

 into double rows of dots. The thin- 

 shelled eggs appear to be deposited 

 before segmentation begins, something 

 rather unusual in this genus. 



Habitat: Spring, Washington Coim- 

 try Club, Chevy Chase, Md. 



Fig. 785. Diplogaster fictor. 



I, side view of femhle; II, head of the 

 same, seen in dorso-ventral view, Ups nearly 

 closed; III, head of the same, lateral view, 

 hps nearly wide open; IV, head of the same, 

 lateral view, hps partially closed; V, front 

 view of mouth, partially dosed; VI, lateral 

 view, posterior portion, of a male specimen; 

 \7I, somewhat diagrammatic jjerspective 

 view showing markings of the cuticula. 



a, one of the lips; 6, one of the six cephalic 

 setae; c, amphid; d, one of the two more or 

 less evertible pharyngeal hook-shaped teeth; 

 e, median esophageal bulb; /, nerve-ring; 

 £, anus; /i, rectum; J, intestine; j, terminus; 

 k, posterior esophageal bulb; /, nerve cells; 

 m, renette cell (?); n, left spiculum; o, lumen 

 of the intestine; p', pre-anal male seta; 

 P'\ P"'> P"", post-anal male setae and papil- 

 lae; q, one of the cells of the intestine; r, 

 accessory piece: s, flexure in anterior ovary; 

 /, blind end of anterior ovary; v, vagina; 

 w, synapsis in egg in the anterior uterus; 

 X, one of the spermatozoa in the vagina; 

 y, uterus; z, vulva. (After Cobb.) 



25 (24) Bulb one, then cardiac, or none; spinneret present 26 



