NO. 6 CLASSIFICATION OF NEMATODES FILIPJEV 29 



within the last few years ; externally they are represented by incon- 

 spicuous slits or even papillae. The caudal glands are absent ; they are 

 replaced in some, if not in all, forms by paired subcaudal glands open- 

 ing on the sides of the tail ; they are probably not homologous with the 

 true caudal glands. In the esophagus there is often a bulb with the 

 masticatory apparatus inside ; a preneural swelling is present in several 

 forms (fig. 61) ; in others it is transformed into a true second bulb, 

 generally called the middle bulb, the posterior or cardiac bulb corre- 

 sponding to that of the other forms (fig. 65) ; in still others the mus- 

 culature is much reduced in the posterior bulb, only the glandular 

 cells being preserved, the only muscular bulb being the anterior one 

 (fig. dy). In Aphelenchus and some other genera the cells of the 

 posterior glandular part of the esophagus are not separated from the 

 intestine by any constriction, so that it appears as though the neural 

 ring is situated around the anterior part of the intestine. In the 

 male genitalia there is often a prominent bursa (figs. 62, 63). The 

 whole organization bears traces of reduction and definitiveness ; the 

 musculature is mostly meromyarian: a sacrifice to the accelerated 

 development characteristic of and indispensable to these saprozoic 

 forms. There seems to be no group in the families previously dis- 

 cussed to which the organization of this order could be closely com- 

 pared with good reason. 



KEY TO FAMILIES OF ANGUILLULATA 



1. (4) Esophagus with or without a bulb. Free-living or 



parasites of plants and insects. 



2. (3) Esophagus with the cardiac bulb Anguillulidae 



3. (2) Esophagus with the middle bulb present or re- 



duced Tylenchidae 



4 (i) Esophagus without bulb, of uniform musculature 

 throughout its length. Parasites of vertebrates. 



5. (6) Syngonic; digenetic with a free-living rhabditoid 



generation Anguillulidae (partim) 



6. (5) Amphigonic; with direct development, rhabditoid 



larvae never reaching free-living maturity Strongylidae 



Subfamilies and Genera of the Family Anguillulidae 

 Subfamily Anguillulinae. 



Genera: Rhabditis Dujardin, 1845 (sg. Rhabditella Cobb, 1929); Rbabdi- 

 toides Goodey, 1929; Asymmetricus Kreis, 1930 (syn. Psendorhabditis 

 Kreis, 1929, preocc.) ; Diploscapter Cobb, 1913 ; Hyalaimns Cobb, 

 1920. 

 Subfamily Steinerneminae. 



Genera: Neoaplectana Steiner, 1929; Steinernema Trzxdi'ssos, 1927c (syn. 

 Steineria Travassos, 1927a, preocc.) ; Hemicycliophora de Man, 1921; 

 Cheilobus Cobb, 1924; Anguillula C. F. Mueller, 1783 (syn. Turba- 

 trix Peters, 1927); Macrolaimus Maupas, 1900; Myolaimus Cobb, 

 1920; Himatidiophila Rahm, 1924. 



