1. INTRODUCTION 5 



interest among zoologists and the question of the systematic position of the 

 Pogonophora was a subject of animated debate. In 1938 Reisinger ascribed 

 Lamellisabella to the Vermes Oligomera (in the sense of Butschli, 1910, and 

 Krumbach, 1937), considering that the Pogonophora took their place along- 

 side the Phoronidea and the Enteropneusta. [It was not yet realized that 

 Siboglinum was related to Lamellisabella.] Then Beklemishev (1944) pointed 

 out that the major features of the organization of Lamellisabella suggested 

 that the Pogonophora should be placed with the Hemichordata, and a 

 comparison of Lamellisabella with the Enteropneusta and with the Ptero- 

 branchia forced him to consider the Pogonophora as an independent primi- 

 tive phylum of the Deuterostomia. Later, when the organization of Lamell- 

 isabella became better known, several of Beklemishev's arguments fell down, 

 but nevertheless the position of the Pogonophora in the classificatory scheme 

 was abundantly confirmed. The idea that Siboglinum was related to the 

 Hemichordata was advanced independently by Dawydoff (1948), on the 

 basis of a detailed analysis of this genus from the data of Caullery. Ulrich 

 (1950), however, after a detailed discussion of the data of Johansson on 

 Lamellisabella, placed the Pogonophora as a distinct phylum of the Archi- 

 coelomata, on a par with the phyla Chaetognatha, Tentaculata, Enteropneusta 

 (= Hemichordata) and Echinodermata. Further grounds for the ascription 

 of the Pogonophora to the Deuterostomia were, however, adduced by Ivanov 

 (1955), who placed the class in a new phylum (which he named the Brachiata), 

 when the architectural plan of the Pogonophora became clearer. 



It is interesting that for rather a long time no one attempted to compare the 

 structure of Siboglinum with that of Lamellisabella, though it was manifest 

 that both of them belonged to the same systematic group (Ivanov, 1951). 



In 1949 Ivanov described a third species of pogonophore — Lamellisabella 

 (or Polybrachia) gorbunovi — this time from the Arctic Ocean. Then the 

 number of known species quickly began to grow, thanks mainly to the ex- 

 peditions of R.V. Vityaz? (1949-1958) to the western parts of the Pacific 

 Ocean. From the collections of R.V. Vityaz? were described first five species 

 and four genera and then an additional twelve species and two genera 

 (Ivanov, 1952, 1957a). The Danish deep-sea expedition of circumnavigation 

 on R.V. Galathea produced yet another new genus — Galathealinum — from 

 the Celebes Sea (Kirkegaard, 1956a). Jagersten (1956) described Siboglinum 

 ekmani from the Skagerrak. Numerous new forms (two new genera, nineteen 

 species) have been described very recently from Soviet expeditions to various 

 seas. Southward and Southward (1958, 1959) have described two new species 

 of Siboglinum, a new species oi Oligobrachia and one of Diplobrachia taken in 



