TABLE fi. 

 Nemi Relationships. Table of Scores. 



N 



R 



E 



No 



No: 



Tu 



Tr 



Ce 



Ac 



Ne 



An 



Ta Ar 



tionable. The earlier view that the "praesoma" did not 

 take part in later development was disproved by May. 

 These points all support the inclusion of the Nemato- 

 morpha in the Aschelmintha. 



If the Nematomorpha were credited unqualifiedly as 

 having molts (No!) then five points more would be 

 scored in comparison with some groups and five deducted 

 from others so that the score series would be Nemata, 

 47; Echinodera, 43; Rotatoria, 42; Tardigrada, 39; Gas- 

 trotricha, 39; Acanthocephala, 36; Annelida, 34; Turbel- 

 larea, 31; Trematodea, 27; Nemerta, 27; Cestodea, 24; 

 Arthropoda, 21. In the reciprocal scoring series the 

 Nematomorpha would be included as showing similarities 

 to the Nemata and Echinodera and just under the break 

 of the Rotatoria, Gastrotricha and Annelida series. These 

 indications of similarity support the two diverse schools 

 of thought, the one which is the more popular (and 

 here the more distinct) placing the Nematomorpha in 

 the Aschelmintha or Nemathelminthes, and the other 

 less popular one which relates the Nematomorpha to the 

 Annelida. 



On the basis of the information obtained from tables 

 4 to 6, it appears that there are three groups of the rank 

 series among the organisms considered (Old group Vermes 

 and Arthropoda). These series are as follows: Paren- 

 chymata (containing the phyla Nemerta, Acanthocephala, 

 and Platyhelmintha), Aschelmintha, and Annelida-Tardi- 

 grada- Arthropoda (Unnamed as far as we know). 



The phylum Nemata, proposed by Cobb (1919), ap- 



parently constitutes a valid group differing from other 

 groups as much as do the more regularly constituted 

 phyla. It is included within the Series Aschelmintha 

 which also contains the phyla Rotatoria, Gastrotricha, 

 Echinodera and Nematomorpha. The name Nematoda 

 may be retained for a class equivalent in extent to the 

 phylum Nemata or it may be dropped. In the latter 

 instance the subclasses Phasmidia and Aphasmidia would 

 take the rank of classes. In many ways the Phasmidia 

 and Aphasmidia are parallel and might be considered 

 twin classes just as the Gastrotricha and Echinodera 

 are twin phyla. The name Nemathelminthes seems to 

 apply to no natural group. 



The position of the Tardigrada within the Annelid- 

 Arthropod series is very clearly substantiated. It is un- 

 fortunate that students of the larger segmented forms 

 do not direct some of their attention to the Tardigrada. 



A family tree (Fig. 146) sums up the conclusions of 

 the scoring in a graphic manner. No attempt is made 

 to express degrees of primitivity or possible ancestry 

 between one group and another. One could, and the 

 writer has, made scoring tables on the basis of "Degree 

 of primitivity," expressed numerically, but first all vari- 

 ations of all organs need to be rationalized and a de- 

 scription of the primitive condition set forth. This is 

 so subjective that we fear to expose it to public con- 

 demnation. 



202 



