NEMATODE PARASITES OF BIRDS 



2. Males usually with a well-developed membranous bursa supported by a sys- 



tem of rays, usually 6 paired rays and a single unpaired median dorsal ray ; 

 or, sometimes, with paired dorsal rays ; rarely without bursa ; buccal 



capsule present or absent ; eggs usually thin-shelled Strongylata, p. 5. 



Males without a well-developed membranous bursa of the type noted 3. 



3. Heteroxenous forms, the larval stages occurring in various intermediate 



hosts ; mouth usually with 2 lips, or a larger number of lips or lobes 

 capable of resolution into 2 basic lips, or without lips ; oviparous, vivi- 

 parous, or ovoviviparous Spirurata, p. 162. 



Monoxenous forms as a rule, exceptional forms (seal ascarids) with inter- 

 mediate hosts ; mouth usually with 3 lips, exceptionally without lips : 

 oviparous 4. 



4. Meromyarian ; males with 1 spicule, at times reduced, imperfectly chitinized, 



or absent Oxyurata (not dealt with in this paper). 



Polymyarian ; males usually with 2 spicules Ascaridata, p. 48. 



Several of the suborders listed above have already been proposed, 

 the Strongylata by Railliet and Henry in 1913 and the Ascaridata 

 and Spirurata in 1915, and the Trichurata by Skrjabin in 1916. It 

 is, therefore, hardly a radical action to recognize these groups or to 

 propose coordinate groups for the nematode groups of coordinate 

 rank and importance. This gradual elevation of groups, which 

 often begins with the splitting of composite species to assemble the 

 resultant species in a genus, is a characteristic feature of taxonomy. 

 It is correlated with the fact that as new species are added at the 

 bottom, newer and larger filing units must be added at the top to 

 accommodate the large number of lower groups and to maintain 

 them as far as possible in their order of relationships and relative 

 importance. In the nematodes the elevation of groups is crowding 

 up generic distinctions to subfamily rank, and thereby forcing up all 

 the groups above. Only the method of experiment, of trial and 

 error in taxonomy, will determine where the movement should stop, 

 but at present it seems advisable and necessary to continue along 

 this line. 



Suborder Strongylata Railliet and Henry, 1913 



Suborder diagnosis. — Bursate nematodes, the bursa a membranous 

 structure on the male tail and primarily a clasping organ for attach- 

 ment to the female. The basic pattern of the rays supporting the 

 bursa is fairly constant and consists of 2 ventral and 3 lateral rays 

 on each side and a dorsal group of 1 externo-dorsal ray on each side 

 and an unpaired median dorsal ray or of 1 externo-dorsal and 1 dor- 

 sal ray or branch of a dorsal ray on each side. The musculature is 

 either polymyarian or meromyarian. The body shape ranges from 

 thick and cylindrical to threadlike or hairlike. The anterior ex- 

 tremity may be straight or curved dorsally or ventrally. A buccal 

 capsule of extremely variable form may be present or it may be 



