56 DISCOVERY REPORTS 



with gonads adjacent to the stomach; with eight narrow radial canals; with numerous tentacles, all 



alike, in a single row; with club-shaped marginal statocysts. 



As a matter of fact, the position of the gonads is variable. In A. australe they are sac-shaped, 

 situated in the proximal parts of the radial canals but distinctly separated from the stomach. In 

 A. antarcticiim they are restricted to the walls of the upper part of the stomach, whereas no gonads 

 are found on the radial canals. If we knew only these two species, we should probably regard them 

 as belonging to two different genera, but as demonstrated below, A. amplum and tetragonium may be 

 regarded as transitional forms. 



In Arctapodema the gonads are radially separated; in Homoeonema, which contains only one species, 



platygonon Browne, the gonads form a continuous band around the base of the stomach, extending 



outwards along the radial canals (see Kramp 1947, p. 17). There is good reason, therefore, to keep 



these two genera apart. 



Arctapodema antarcticum (VanhoflFen 19 12) 



(Text-fig. 9) 



1912a Isonema antarcticum Vanhoffen, p. 375. Text-figs. 8-9. 



1936 Arctapodema antarcticum Ranson, p. 157. 



Occurrence: St. 1718. 25. iii. 36. 64° 22' 36" S, 106° 33' 18" E. Off Knox Land, Antarctica. Net: TYFB 900- 



550 m. I specimen. 

 St. 1749. 24. iv. 36. 32° 04' 06" S, 77° 59' 36" E. Between South Africa and Australia. Net: TYFB 1050-600 m. 



I specimen. 

 St. 1838. 12. X. 36. 57° 10' 12" S, 30° 42' 30" W. East of the South Sandwich Islands. Net: TYF 70 B 750-250 m. 



3 specimens. 

 St. 1917. 3. xii. 36. 53° 48' 42" S, 46° 27' 42" W. Near Shag Rocks. Net: TYFB 1400-1000 m. i specimen. 

 St. 1919. 4. xii. 36. 54° 02' 54" S, 42° 10' 48" W. West of Shag Rocks. Net: TYFB 1800-1300 m. i specimen. 



The specimens have the following diameters: St. 1718: 15 mm.; St. 1749: about 13 mm.; St. 1838: 



14, 14 and 16 mm.; St. 1917: 11 mm.; St. 1919: 16 mm. The tentacles could only be counted in two 



of the specimens (Stns 1718 and 1838), both had about 112 tentacles. The manubrium is cylindrical, 



and the gonads occupy the proximal one-third to one-half of the stomach; they are not ring-shaped 



as stated by Vanhoffen, they are interrupted in the four perradial corners of the stomach, so that there 



are four interradial gonads; this applies to female as well as male gonads. In all other regards the 



specimens agree perfectly with Vanhoffen's description and figure. 



Distribution. Up to now this species has been known only from the neighbourhood of the Gauss 



Station, in about 90° E near the Antarctic Continent. It is now seen to have a far more extensive 



distribution in antarctic waters, and it has also been found in latitude 32° S in the Indian Ocean, 



about mid-way between South Africa and South Australia (see chart, text-fig. 9). It belongs to the 



deep water-layers. 



Arctapodema amplum (Vanhoffen 1902) 



(PI. V, fig. 4, text-fig. 9) 



19026 Homoeonema amplum Vanhoffen, p. 65. PI. 10, fig. 21; PI. 11, figs. 24, 26, 27. 



19066 Isonema amplum Maas, p. 5. PI. i, figs, i, 2, 7; PI. 2, figs. 8-12; PI. 3, figs. 14-20. 



1907 Arctapodema amplum Dall, p. 661. 



1910 Homoeonema amplum Mayer, p. 387. Figs. 236-7. 



1912a Isonema amplum Vanhoffen, p. 374. Text-figs. 4-7. 



1913 Pantachogon amplum Bigelow, p. 44. 



1936 Homoeonema platygonon Thiel, p. 26, in part. 



1936 Arctapodema amplum Ranson, p. 158. PI. 2, fig. 17. 



1938 Arctapodema najadis Pell, p. 926. 



1955 Arctapodema amplum Kramp, p. 273. 



