NO. 6 CLASSIFICATION OF NEMATODES FILIPJEV 4I 



Linne, i.e., the registration of similarities and dissimilarities, only a 

 little and superficially colored by the theory of evolution. The simi- 

 larities alone have a value for the building of a natural system. The 

 absence of some distinct feature or the presence of one, should not 

 be a cause of the exclusion of some form from a group when other 

 characters are similar. No character is important by itself, but only 

 in its more or less wide occurrence among similar forms. For this 

 reason I do not hesitate to range a spiral-amphid Tripyloides among 

 other pocket-amphid Enoplata, and because of these principles it 

 seems to me wise to class the Strongylidae within the Anguillulata. 



Each systematic arrangement of a group, with very rare ex- 

 ceptions, passes, it seems, through three stages. The first is that of 

 chaos, the second is the putting of the closely similar side by side, 

 and the third is a definite classification upon the basis of real resem- 

 blances. Stiles and Hassall (1926) are, of course, right in saying 

 that a natural system of the Nematoda is in the stage of making ; it 

 seems that we are gradually passing through the second stage, and 

 are rather in it than in the first one. 



LITERATURE CITED^ 

 Allgen, C. 



1927. Freilebende marine Neinatoden von der Kiiste Tasmaniens. Zool. 



Anz., vol. Ji, pt. g-io, pp. 1^7-217, figs. 1-2. Leipzig. 

 1929a. Neue freilebende marine Nematoden von der West-Kiiste Schwe- 



dens. Zool. Jahrb., Abt. Sj'St., vol. 57, pp. 431-496, figs. 1-47. 



Jena. 

 1929b. Freilebende marine Nematoden aus den Umgebungen der staat- 



lichen zoologischen Station Kristineberg an der West-Kiiste 



Schwedens. Cap. Zool., vol. 2, no. 8, pp. 1-53, pis. 1-4. The 



Hague. 

 1929c. t)ber einige freilebende marine Nematoden von der Macquariein- 



sel. Zool. Anz., vol. 84, pt. 5-6, pp. I19-126, figs. 1-3. Leipzig. 

 1930a. Conolaimella, ein neues Genus mariner Nematoden von der West- 

 Kiiste Schwedens. Ibid., vol. 88, pt. 5-6, pp. 138-141, figs. 1-4. 

 1930b. Freilebende marine Nematoden von der Stateninsel (Feuerland- 



Archipel) I. Ibid., vol. 89, pt. 7-10, pp. 246-258, figs. 1-4. 

 1930C. Idem, II. Vol. 90, pp. 27-38, figs. 1-6. 

 Artigas, p. 



1926a. Nematoidos de Invertebrades. I. Bol. Biol., no. i, pp. 1-13, figs. 



1-25. Sao Paulo. 

 1926b. Idem, II, no. 2, pp. 38-41, figs. 1-9. 

 1926c. Idem, III, no. 3, pp. 59-71, figs. 1-15. 

 I926d. Idem, IV, no. 4, pp. 97-110, figs. 1-16. 



1927. Idem, V, no. lO, pp. 209-211, figs. 1-2. 



1928. Idem, VI, no. 12, pp. 71-75, figs. 1-3. 



5 Owing to delays for various reasons in the publication of this paper, the 

 literature after 1930 is not included in this list. 



