Pelagic Tunicata — Bary 
115 
Charts of the occurrences of P. atlanticum 
(Fig. 18 f-h) indicate that it may be entering 
coastal areas in water of subantarctic origin, but 
when plotted against salinity and temperature 
(Fig. 22) the collections are seen to occur in- 
discriminately in coastal and "Northern” Sub- 
antarctic waters. Specimens were also collected 
from stations near Station 826 (not recorded 
herein) in the subantarctic. Such occurrences 
agree with Sewell (1953: 85) who says that 
P. atlanticum is common throughout the oceans 
between temperatures of 7° and 30° C. 
Doliolum ( Dolioletta ) valdiviae 
Dolioletta valdiviae was present in that part 
of Foveaux Strait (Fig. 18^, /) in which coastal 
water is believed to be most directly influenced 
by water of subtropical origin (Bary, 1959^) . 
Its few occurrences when plotted against salinity 
and temperature (Fig. 22) are in the warmest 
water, which together with its absence from 
samples elsewhere about southern New Zealand, 
suggest a warm-water origin for the species. 
More data on occurrences of the species about 
New Zealand and information on its distribu- 
tion elsewhere are needed. 
Iasis zonaria 
This is a widely distributed species which 
Sewell (1953) regards as being carried from 
tropical to colder waters by currents. However, 
Thompson (1948) believes the species is more 
usually found in the deeper, colder waters in 
tropical or subtropical regions. It was plentiful 
off southeastern Australia (Thompson), but was 
commonest from the temperate waters of the 
Tasmanian area. In each year from 1939 to 1941 
it decreased towards the north and this was in- 
terpreted as resulting from the increasing effects 
of subtropical conditions northwards. Russell 
and Colman (1935) recorded one specimen of 
the solitary form from 200 m. outside the Bar- 
rier Reef; Dakin and Colefax (1940) recorded 
specimens for September only, which is in 
agreement with Thompson’s statement that 
the period of greatest abundance is in the 
spring (August or September to November or 
December ) . 
Iasis zonaria is scarce in Lachlan samples (Fig. 
18 d) . Occurrences, when plotted against salinity 
and temperature (Fig. 21) indicate a restricted 
range of salinity (ca. 34 °/oo to 34.5 °/oo) and 
a preference for lower temperatures, features 
suggesting the species was collected from water 
of subantarctic origin. This would lend sup- 
port to Thompson’s belief that the species is a 
temperate-water one. The New Zealand records 
are too few to be more than suggestive. 
Thalia democratica 
Metcalf (1918) distinguishes between west- 
ern Pacific and Atlantic forms of aggregate 
specimens of Thalia democratica. The Pacific 
form possesses a variable number of tubular test 
processes, and the test is rounded posteriorly to 
the alimentary "nucleus.” The Atlantic form 
possesses few, and shorter, tubular processes and 
the test is pointed posteriorly. Sewell (1953) 
points out, however, that the test varies con- 
siderably among his specimens from the Indian 
Ocean. The Lachlan specimens had from zero to 
several tubular processes, most of which were 
short; none possessed a posterior process ap- 
proaching the length illustrated by Metcalf for 
specimens from the Philippine Islands. This, and 
the pointed test posterior to the "nucleus” sug- 
gest they may have been of the "Atlantic” form. 
Thompson (1948) reported that the "West 
Pacific” form predominated in a collection from 
Kaipara Harbour, northwestern North Island, 
and it has since been collected in Hauraki Gulf 
on the east coast of North Island (unpublished 
data). Northern New Zealand is predominantly 
influenced by subtropical waters (and on the 
east coast, possibly even by water of tropical 
origin) and probably this form has been trans- 
ported into these areas in these waters. In the 
south, the water is cooler and preponderantly of 
subantarctic origin. The distinctions in the 
shapes of the tests between north (Thompson’s 
FIG. 20. Generalised Temperature-Salinity-Plankton diagram of the sampled area. Only the plankton sta- 
tions are shown; they are differentiated into series of stations which in turn are shown individually in Figures 
18, 19- "Areas of chief concentration” (as demonstrated by all of the indicator species utilised) are also shown. 
Station numbers in italics are night stations; in italics and underlined, are dawn or dusk stations; unmarked 
are daylight stations. 
