226 KEY TO THE MALES 



Ends of the spicula cephalated by expansion ffew Genera 



Width of the spicula not uniform 



Length of spic. equal to 2 anal body diams.; -m-; tail finally oylindroid; spin.? .Gonionchus 97 

 Length of spioula equal to IJ-li anal body diameters 



Apophysis to ace. backward-pointing; spic. 1J long as anal body diam; -m-.Coinonema 42 

 Apophysis to accessory none 



Accessories 2, bending away from the spicula; spinneret unarmed; -m Zalonema 57 



Accessory 1, parallel to the spicula; spinneret armed; -m-(?) Leptonemella 21 



Width of the spicula more or less uniform 

 Length of the spicula about 1-1$ times the anal body diameter 

 Form of the spicula only slightly arcuate 



Tail diminished to a narrow terminus; -m-; accessory i as long as spicula. .Zygonemella 26 

 Tail not diminished t9 a narrow terminus; accessory j long as spicula, sigmoid . Rhinema 114 

 Form of the spicula distinctly arcuate, or bent 

 Apophysis to the accessory present 



Term, swol.; spin, rounded, unarmed; -m; proximal 3rd of spic. straight. Campylaimus 5 

 Terminus apiculate; spinneret acute, armed; -m-; ace. soon bends away. . (Coinonema) 42 

 Apophysis to the accessory none 



Spicula not L-shaped; ace. slender, parallel, \ &s long as the spicula; ^m.Alaimella 1 

 Spicula L-shaped; striae resolvable into elements 



Accessory f as long as dark-colored spicula; tail without wings Omicronema 50 



Accessory \ as long as spicula; tail with wings Xyala 72 



Length of the spicula about twice to thrice that of anal body diameter (Tripylium, 1 f) 

 Form of spic. normally straightish, arcuate in strong ace. ; spinneret blunt. (LeptoQastrella) 28 

 Form of the spicula arcuate 

 Apophysis to the accessory present 



The accessory surrounds posterior J of hamate spicula; -m; caudal setae few.Iotadorus 115 

 Theaccessory parallel to narrow spicula; -m-; caudal setae many, in 4 TovfS.Pepsonema 77 

 Apophysis to the accessory none 



Accessory tub., strongly developed, enveloping spic.; numer. setae; -m.LeptoQastrella 28 

 Accessory not tubular 



Accessory bends away from spic., J long as spic.; -m; term, blunt, armed. Apodontium 62 

 Accessory parallel to the spicula 



Anus 85; ace. surrounds laterally bent, dark-col, spic.; -m-; spin, armed. Daptonema 66 

 Anus more than 90; spicula not laterally bent, not dark-colored; spinneret unarmed 



Spinneret blunt, tubular; anus 93; -m; accessory f as long as spicula Tripylium 71 



Spinneret conical, plain; anus 96; -m; accessory parallel to distal halves. Psevdonchus 58 



THE NEMA FORMULA 



Nema dimensions sometimes vary perceptibly with varying technique. 



As a rule, information conveyed in the keys, formulae and illustra- 

 tions is not repeated elsewhere. Following other authors, the measure- 

 ments for the ovaries are given separately instead of in the form of a 

 single measurement as formerly. Furthermore, the oblique stroke indi- 

 cating the presence and position of the excretory pore is here, in No. 

 IX, placed below the formula line, the assumption being that the for- 

 mula shows the nema ventral side down. The general form of the spic- 

 ula and accessories is shown in the formula for the male, as is also the 

 presence, number and position of the supplements, indicated by small 

 suffixes before and after the anal measurement figure. The spicula dia- 

 grams are of three different degrees of curvature, indicating nearly 

 straight, arcuate and strongly arcuate spicula. The nature of the prox- 

 imal ends of the spicula is indicated, i. e. whether cephalated, and if 

 cephalated, whether by contraction, constriction or expansion. Also, 

 if it exists, the presence of an apophysis to the gubernaculum is indi- 

 cated. The short, horizontal marks indicating the wings and the pres- 

 ence and relative diameter of the oesophageal swellings are only dotted 

 when these features are not of a pronounced nature. The mark indi- 

 cating the presence of a spinneret is either plain or so conventional- 

 ized as to indicate that the spinneret is supplied with setae. The 

 absence of any particular mark in the formula is practically always 

 to be taken as indicating that the particular feature in question is 

 non-existent. Doubt is expressed by a question mark. The reason 



