6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



All this speaks in my opinion for the primitiveness of free-living 

 nematodes and especially the marine ones. 



But we hardly could point to these differences for a primary 

 division into two orders or subclasses as was proposed by Perrier 

 and apparently on ground of convenience by Stiles and Hassall 

 (1926). Bastian's classical words that the organization of free- 

 living forms "as a whole, differs in no obvious or important man- 

 ner from that of their parasitic kindred" hold true today. More- 

 over, the differences between systematic groups within the broad 

 groups of parasites and free-living nematodes, and an apparent 

 absence of intermediate forms between them, demands a direct 

 division of Nematoda into several orders without any subclasses. 

 If one wishes to use such a division, then the dividing line must be 

 drawn between the Anguillulata and the other free-living forms, 

 rather than between the Anguillulata and the parasitic ones.^ 



A proposed classification is presented herewith : 



Class NEMATODA 



Order ENOPLATA Order ANGUILLULATA 

 Family Enoplidae Family Anguillulidae 



Trilobldae Tylenchidae 



Dorylaimidae Strongylidae 



Mermitidae 



Order CHROMADORATA Order OXYURATA 



Family Camacolaimidae Order ASCARIDATA 



Plectidae Order SPIRURATA 



Chromadoridae Order FILARIATA 



Order DESMOSCOLECATA Order DIOCTOPHYMATA 



Order MONHYSTERATA Order TRICHURATA 

 Family Monhysteridae 

 Linhomoeidae 



KEY TO ORDERS OF NEMATODA 



1. (8) Tail with tail glands and spinneret (when without, 



then with amphids pocketlike). Amphids of various 

 forms, mostly well developed. Mostly free-living, 

 nonsaprozoic. 



2. (3) Amphids pocketlike. Cuticle smooth. Bulb absent. 



Ovaria reflexed. Free-living, marine or fresh-water 



and soil-inhabiting, or parasites of insects Enoplata 



3. (2) Amphids spiral or of derived form; circular, bubble- 



like, horseshoe-shaped, or transverse and slitlike. 



II 



^AU parasitic forms studied by Martini (1906, 1909) have a primary 

 division of the epidermis into six cell rows, but the few Enoplata studied by 

 Retzius and by Filipjev (1912, 1923) have eight. The scarcity of forms 

 studied does not as yet permit one to draw any decisive conclusions. 



