CLASSIFICATION OF THE ANIMAL KINGDOM 



28 



and the nature of the material of this exo- 

 skeleton is not known. It is not possible to 

 say definitely that the graptolites are 

 coelenterates, because the nature of the 

 body cavity is not known, but there is no 

 evidence that it is not a coelenteron. The 

 graptolites may thus reasonably be in- 

 cluded in the Coelenterata, even placed in 

 the Hydrozoa because of general similari- 

 ties, but information is simply lacking that 

 would enable one to say that they did have 

 the features of the coelenterates. 



Inasmuch as there is some evidence of 

 bilaterality, the skeletal tubes are different 

 from those of Hydrozoa in manner of for- 

 mation, and the almost universal form of 

 the colonies is unmatched in the Hydrozoa, 

 it is also reasonable to emphasize the dif- 

 ferences by separating the group from the 

 Hydrozoa as a class. Because of the lack of 

 knowledge of all soft-part features and the 

 possibility that some of these also are with- 

 out counterpart in the Coelenterata, it is 

 here preferred to emphasize this uncer- 

 tainty by separating the group as a phylum 

 distinct from Coelenterata. 



The class Hydrozoa is already one of 

 the most diverse in the Animal Kingdom. 

 It seems undesirable to increase further its 

 heterogeneity by including an additional 

 series of different features. The distinctive 

 features of the Coelenterata cannot be ad- 

 duced to help us with the graptolites, so 

 these fossils cannot be included in that 

 phylum upon any firm basis. 



Conularida. The same arguments as ap- 

 plied above to the Graptozoa are cogent 

 for the separation of the Conularida as a 

 separate phylum also. Apparently no coe- 

 lenterates have a chitinophosphatic skele- 

 ton, which fact alone makes the inclusion 

 of these animals in that phylum unsatisfac- 

 tory. Of course, here -Iso there is no direct 

 evidence that the animals were actually 

 coelenterate in nature. 



This group has recently been assigned 

 to the Scyphozoa, although also placed 

 sometimes as a phylum near the Annelida 

 or as a member of some other phylum. Al- 

 though quite easily restored to look very 

 much like elongate scyphozoans, the fossil 

 remains of these animals show consistent 

 differences in the steep-sided pyramidal 

 form with four distinct sides, the closing 

 of the aperture by lobes of the side faces, 

 and the chitinophosphatic nature of the 

 periderm. The arguments in the Treatise 

 (F) for combining these with the Scypho- 

 zoa seem very weak. 



Coelenterata. In some recent works (es- 

 pecially Hyman, 1940) this phylum has 

 been called Cnidaria because Coelenterata 

 has at other times included such groups as 

 Ctenophora and Porifera. This reason for 

 abandoning the universally known name 

 Coelenterata would, if applied to other 

 modern phylum concepts, result in chang- 

 ing most of the familiar names, including 

 Porifera, Annelida, Arthropoda, Hemi- 

 chordata, and Chordata. Such a change 

 cannot, in the opinion of the writer, be jus- 

 tified by any benefits resulting therefrom. 

 If it is thought to be necessary, the prior 

 name Nematozoa would also have to be 

 considered. (Furthermore, inclusion of 

 the Graptozoa or Conularida (as in Hy- 

 man) would likewise necessitate a change 

 in the phylum name, by this same argu- 

 ment.) 



Aschelminthes. The proposal of this name 

 by Hyman (1940) for all of the Pseudo- 

 coelomata except the Entoprocta has been 

 adopted by some later works, but her alter- 

 nate conclusion that the subphyla each be 

 treated as a separate phylum has also been 

 followed by some. It is surely premature to 

 claim that the Aschelminthes has been 

 conclusively accepted. Hyman (1951) re- 

 moves one of the original seven groups 

 (Acanthocephala) as a separate phylum. 



The definition given for the emended 

 phylum Aschelminthes in 1951 contains 

 no clear-cut distinctions. Unless such ex- 

 ist, the supposed phylum must be con- 

 cluded to be an indefinable assemblage. 

 The fact that the included subgroups are 

 mostly small and less well known is of no 

 value in determining whether they are 

 phyla, subphyla, or classes. It is here be- 

 lieved that they are adequately distinct by 

 clear-cut features of fundamental nature 

 (body plan, ciliation, "segmentation" of 

 cuticle, presence of jaws, presence of flame 

 bulbs or solenocytes, musculature, nature 

 of nervous system, etc.) to be considered 

 separate phyla. 



Nemathelminthes and Trochelminthes. 

 These two names were formerly applied to 

 the thread-like and the ciliated animals 

 more recently combined into the Aschel- 

 minthes. These groupings are also difficult 

 to define. It is therefore preferred to treat 

 their components as separate phyla. Nema- 

 thelminthes usually included the Nema- 

 toda, Gordiacea, Acanthocephala, and 

 sometimes the Chaetognatha. The Troch- 

 elminthes included the Rotifera and 

 Gastrotricha. 



