216 ORDERS AND CLASSES OF NEMAS 



the aponchs and the synonchs, and having three usually equal onchia, 

 movable in a direction parallel to the body axis; the Aponchia, in which 

 the onchia, separate and nearly always three or six in number, have an 

 outward stroke; and the Triplonchia, having a spear composed of three 

 more or less equal, slender onchial elements which have become amal- 

 gamated. The heteronchian orders are, Axonchia, having a single 

 axial onchium or spear, and the Anaxonchia, in which the main onchium 

 is not axial and may or may not be accompanied by one or two others, 

 usually of smaller size. 



Onchia and odontia seem more or less mutually exclusive, but the 

 presence of one does not necessarily exclude the presence of the other. 

 When both are present, experience appears to indicate clearly that the 

 onchia are the more advantageously used as a guide to broad relation- 

 ships. 



In a later publication the proposed orders will be further denned by 

 describing new type genera. In the meantime, the following table 

 gives a tentative assignment of a few known genera, for explanatory 

 purposes only. Reference to families composing the orders is omitted, 

 because it appears to me after studying a very large number of unde- 

 scribed species in addition to those described, that a number of the 

 families that have from tune to time been proposed may have to be 

 recast. 



Order Genus Order . , Genus 



LITINIA Bastiana SYNONCHIA Enoplus 



BOLBINIA , Laxus MESONCHIA Fimbrilla (?) 



CYTOLAIMIA. .. Monhystera APONCHIA Chromadorella 



ISOLAIMIA Rhabdolaimus TRIPLONCHIA Tylenchus 



POLYLAIMIA.. . Bathylaimus, Plectus AXONCHIA Dorylaimus 



APODONTIA.. . . Axonolaimus ANAXONCHIA Oncholaimus 



SYNODONTIA.. Teratocephalus 



The above linear tabular arrangements of the orders do not bring 

 out fully the natural relationships of the different groups. These 

 relationships will be discussed more fully later. 



While the nomenclature here proposed is dominated by a few linguis- 

 tic roots, it of course by no means follows that in assigning genera to 

 the orders designated, due attention should not be given to other por- 

 tions of the anatomy than those indicated by the nomenclature. This 

 is a commonplace of taxonomy. The relationships of an organism are 

 fully disclosed only on consideration of all its parts, and undue weight 

 given to a particular feature will here, as elsewhere, result in confusion. 



