29 



Nematoda. Hyman is followed here in re- 

 jecting recent proposals to change this 

 name to Nemata. 



Gordiacea. The best form of this name at 

 the phylum level is a moot question. Little 

 is gained but confusion by using Nemato- 

 morpha, whereas Gordioidea has generally 

 been used at the class or order level. Gor- 

 diacea seems to remain as the most distinc- 

 tive phylum name. 



Calyssozoa / Endoprocta. Entoprocta is 

 accepted by Hyman for this group, but this 

 name (or the more distinctive spelling 

 Endoprocta) is much more often applied 

 at the class level. Calyssozoa was proposed 

 originally (and followed by Kamptozoa) 

 for the group as a phylum. Inasmuch as 

 names are needed at both levels, Calys- 

 sozoa is accepted here for the phylum and 

 Endoprocta for the single class. (The 

 spellings Endoprocta and Entoprocta are 

 both ascribed to Nitsche (1870). Both 

 have been used extensively, but the former 

 is more distinct from Ectoprocta and is 

 therefore adopted here.) 



Myzostomida. This peculiar and little- 

 known group has previously been listed as 

 a class of Annelida, as a subclass of 

 Chaetopoda, or as part of the Polychaeta, 

 but apparently never as a phylum. 



These animals are disc-shaped, are 

 non-segmented although with some paired 

 organs, have jfive pairs of ventral append- 

 ages and four pairs of suckers, have ten or 

 more pairs of marginal cirri or tentacles, 

 lack blood-vascular and respiratory sys- 

 tems as well as multiple nephridia, have the 

 central nervous system consisting of a sin- 

 gle large ventral stellate ganglion and two 

 nerve rings around the oesophagus and 

 pharynx, have a complete digestive tract 

 but with the stomach branching through- 

 out the body, and have a trochosphere 

 larva. These features would make the An- 

 nelida impossible to diagnose, and they re- 

 sult in an animal whose peculiarities are 

 only obscured by inclusion in the An- 

 neUda. 



Prenant (1960) in the Traite concludes 

 that these animals are annelids but suffi- 

 ciently distinct to be made a class. It is 

 here believed that the features cited by 

 Prenant make it necessary to remove the 

 Myzostomida from the Annelida, just as 

 the Sipunculoidea and Echiuroidea had 

 previously been removed. 



Myzostomids are reported from sev- 

 eral geologic eras. As these are known only 



Notes on Subkingdoms and Phyla 



from scars or galls, they cannot be as- 

 signed to orders. 



Protarthropoda. The inclusion of Tardi- 

 grada, Onychophora, and Pentastomida in 

 the Arthropoda as a subphylum (Pro- 

 tarthropoda, Pararthropoda, or Oncopoda) 

 has been done, in every case traced out, 

 without direct consideration of whether 

 they have the basic features of arthropods, 

 or whether the resulting agglomeration 

 can be defined. Apparently it cannot be 

 defined, and these three groups individually 

 have only a few of the basic arthropod fea- 

 tures. Until more correlation is demon- 

 strated, it is held that they cannot reasona- 

 bly be combined with the Arthropoda. 



Tardigrada. This group is generally 

 placed in either the Aschelminthes or the 

 Arthropoda. Either position is untenable 

 if Cuenot (1949) is correct in asserting 

 that the animals are coelomate and entero- 

 coelous. It is distinguished from Onycho- 

 phora and Pentastomida, as well as Ar- 

 thropoda, by features of considerable im- 

 portance. It is certainly entitled to phylum 

 status, even if the correct position for the 

 phylum is still unknown. 



Pentastomida. This group is generally 

 placed in the Arthropoda, sometimes even 

 in the order Acarida. Some of its charac- 

 ters have been ascribed to parasitic degen- 

 eration. They apparently have no cilia, do 

 have a chitinous cuticle, and do have an 

 arthropod type of nervous system. They 

 lack an exoskeleton, jointed appendages, 

 Malpighian tubules or coxal glands, circu- 

 latory organs, tracheae, and nephridia, and 

 their appendages are of the type seen in 

 the Onychophora and the Tardigrada. 



As it would be impossible to place 

 these definitely in any class of arthropods, 

 and since they lack many arthropod fea- 

 tures, it seems best to emphasize their dif- 

 ferences by treating them as a separate 

 phylum. 



Hemichordata {Branchiotremata, Adelo- 

 chorda). Nearly all recent classifications 

 recognize a phylum Hemichordata that in- 

 cludes the Enteropneusta, the Pterobran- 

 chia, and perhaps such other groups as the 

 Graptozoa. A good example of this is 

 Hyman (1959). It is difficult to understand 

 this grouping when every attempt at defi- 

 nition consists primarily of variable or 

 relative characters. The components are so 

 distinct that Hyman can only discuss them 

 separately. Almost none of her statements 

 apply throughout the phylum. 



In this situation we only obscure the 



