PTEROPODA, ECHINODERMATA AND TUNICATA 227 



Very few were taken in May off the north-east coast of South Georgia, when its place 

 was taken by L. balea. 



It was not taken in large numbers by the N 70 V nets, but nevertheless from these 

 results we can obtain a good idea of its vertical distribution as shown in Table XXXVI. 



It will be seen that it is an inhabitant of the cold surface layer. The table should be 

 compared with the charts of temperature and salinity in Figs. 7 and 8. It is also 

 common in the cold polar currents of the Arctic. There are indications that this species 

 makes a diurnal vertical migration : this is discussed and illustrated on pp. 240 and 257. 



It has been commonly taken in the plankton catches of a number of Antarctic expedi- 

 tions: Belgica, 1 Southern Cross, 2 National Antarctic (Discovery) 3 Gauss 4 and Terra 

 Nova. 5 



A complete record of its occurrence is given in Appendix II. 



Limacina juv. Specimens of Limacina too young to identify were abundant, particu- 

 larly to the west of South Georgia. A record of their occurrence is given in Appendix II. 



Spongiobranchea australis, d'Orbigny. This species was widely distributed throughout 

 the area but was never abundant. It has been taken previously by the Challenger, 7 

 Belgica, 1 Southern Cross, 2 National Antarctic (Discovery), 3 Gauss, 4 Terra Nova 5 and 

 Aurora 6 Expeditions. A complete record of its occurrence is given in Appendix II. 



ECHINODERMATA 



The almost complete absence of any larval forms of bottom-living animals except 

 Crustacea was a striking feature of the plankton samples throughout the area. This 

 feature has been noted by many previous Antarctic expeditions, and many examples of 

 animals, whose relations in other waters possess pelagic larval stages, have been de- 

 scribed rearing their young in protective brood pouches. This phenomenon will be 

 further discussed in relation to the hypothesis of animal exclusion in a laterpartonp. 358. 

 The only Echinoderm larva met with was a single specimen of the large and beautiful 

 Aiiricalaria antarctica, MacBride, taken at St. 125 at a depth of 250-100 m. A single 

 specimen of this larva was taken by the National Antarctic (Discovery) Expedition 

 (MacBride, 1912), and fifteen specimens by the Gauss (Mortensen, 1913) at twelve 

 Antarctic stations. 



TUNICATA 



Salpafusiformis, var. aspera (Cham.). Salps formed a prominent feature of the plank- 

 ton of the area, often occurring in enormous numbers, and at times making the sorting 

 of the catch very difficult. At St. WS 38 10,730 were taken in a single surface haul with 

 the N 100 H net. They were all of one species, S.fusiformis, and all those examined 

 closely appeared to belong to the form aspera, but other forms may have been present. 



1 Pelseneer (1903). 2 Smith (1902). 3 Eliot (1907). 



4 Meisenheimer (1905). 5 Massy (1920). u Hedley (1916). 



7 Pelseneer (1887). 



