14. SYSTEMATIC POSITION OF THE POGONOPHORA 135 



we can find no grounds for associating the Pogonophora with the Phoronidea. 

 The tentacular crown of Phoronis, which at first glance so closely resembles 

 that of Pogonophora, is borne on the mesosoma, while the tentacles of the 

 latter group are protosomal structures. The nephridia of the Phoronidea, in 

 distinction to the protosomal coelomoducts of the Pogonophora, belong 

 morphologically to the metasoma. The blood-vascular and nervous systems 

 of the two groups are sharply distinguished in their fine structure. It has been 

 pointed out by Reisinger (1938) and Johansson (1939) that the median 

 cephalic lobe of Pogonophora might be compared to the epistome ofPhoronis. 

 It is impossible, however, not to agree with Jagersten (1956) that the 

 foundations for this comparison are as slight as for the recognition of an 

 epistome in the Enteropneusta. 



Are they related to the Deuterostomia ? 



Johansson, recognizing that Lamellisabella belonged to a separate class 

 Pogonophora, ascribed it to the superphylum Vermes Oligomera adopted 

 first by Biitschli (1910) and later by Krumbach (1937). It is gradually be- 

 coming clear, however, that Biitschli had lumped together too heterogeneous 

 and artificial a group to form the Oligomera. Johansson pointed out the 

 impossibility of associating the Pogonophora with the Phoronidea and that 

 their common inclusion in the Tentaculata would not bear examination, 

 since in the composition of the Oligomera Biitschli also included the Chaetog- 

 natha and the Branchiotrema (= Hemichordata), groups which are totally 

 diverse. 



One of the essential defects of the Biitschli-Krumbach system is the 

 unjustified break between the Hemichordata and the Echinodermata and 

 Chordata to which they are clearly related. The proximity of the Hemi- 

 chordata to the prototypes of the echinoderms and chordates, and the 

 essentially common path of embryonic development in these groups, which 

 led to their being united under the name Deuterostomia, was already 

 obvious by the time of Hatschek (1888) and Grobben (1904) and was particu- 

 larly well demonstrated by the work of MacBride (1914), Fedotov (1923) and 

 Beklemishev (1951). Each of these three groups possesses its own structural 

 plan and, within the Deuterostomia, merits the rank of an independent 

 phylum. 



A few zoologists, while not objecting in principle to the division of the 

 Metazoa into Protostomia and Deuterostomia, reckon on formal grounds 

 that these terms are themselves inappropriate. Thus Manton (1958), in her 

 report of the work of Ivanov (1957b) on the embryology of Pogonophora, 



