318 
PACIFIC SCIENCE, Vol. XIII, October, 1959 
trated. All samples have been quantitatively 
analysed. 
The method of the temperature-salinity- 
plankton (T-S-P) diagram (Bary, 1959) is 
used here to elucidate the distributions of 
species. Occurrences of species are plotted in 
the intercepts of the temperatures and salini- 
ties of the stations at which they were cap- 
tured. Species are thus related to the 
hydrological conditions as indicated by these 
properties. The water-envelope (Figs. 1-4) 
surrounds the intercepts of all the tempera- 
tures and salinities of the surface waters in the 
sampled areas, but Figure 1 shows only those 
for plankton stations. The hydrology of the 
area and the relationships of these waters are 
illustrated and discussed by Bary (1959). 
T-S-P diagrams of the five commonly oc- 
curring amphipods are shown in Figures 3 
and 4. The geographical distributions of these 
species in relation to temperatures (Figs. 5, 6) 
are discussed and interpreted in the light of 
information derived from the T-S-P dia- 
grams. The stations have been subdivided 
into several series, and each of these is as near 
as possible a synoptic series and a geographic 
unit. The geographical distribution of the 
subantarctic species and the coastal-subtrop- 
ical species are charted for each series. Rare 
species are charted according to the water 
properties with which they are associated in 
the T-S-P diagram (Fig. 2). Thus, Vibilia 
stebhingi (?), at Station 210, is shown to be in 
water of subantarctic origin in the T-S-P dia- 
gram; therefore, the appropriate geographical 
chart is that which concerns other subantarctic 
species (Fig. 5g) . As well, the rare species are 
listed in Table 1 and appreciations are made 
of their distributions as recorded by other in- 
vestigators, and as indicated by the relation- 
ships exhibited in the T-S-P diagrams. In the 
charts they are shown together at Station 79 
among the subtropical species. 
DISTRIBUTION 
Indicator groups of species were selected 
previously (Bary, 1959) for coastal water (one 
group), for water originating in the sub- 
tropical region (one group), and for the sub- 
antarctic region (two groups, a Southern 
Group for cold water, and a Northern Group 
for that cold water which has undergone a 
temperature increase in its progress north- 
ward). The cohesion of each of these groups 
in the T-S-P diagrams can only be interpreted 
as being due to a correlation between the dis- 
tribution of the individual species composing 
the group and the properties of the water 
body which they inhabit and of which they 
are indicators. The area of chief concentration 
of each indicator group of species is shown in 
Figure 2 by lining-in; there are, however, no 
species of the Northern Group among the 
Amphipoda. The stippled arrows indicate the 
routes (within the diagram) along which 
oceanic species are believed to be penetrating 
towards coastal waters. These routes closely 
coincide with the direction of water move- 
ments as deduced from the corresponding 
T-S diagram of the surface waters (Fig. 1). 
The cold-water Amphipoda are repre- 
sented solely by species of the Southern 
Subantarctic Group (Fig. 3). Large numbers 
of Parathemisto {Euthemisto) gaudkhaudit were ^ 
captured; there were fewer specimens of Cyl- 
lopus magellanicus, and C. macroph was rare. 
Both the numbers of these oceanic species, 
and the frequency of their occurrences de- 
creased in coastal waters, probably as a result 
of their being transferred into relatively ad- 
verse conditions. However, the greater num- 
ber of the stations in coastal waters were |t 
occupied in daylight (Fig. 1) which may |l 
contribute towards the taking of fewer speci- i! 
mens (this feature is discussed by Bary, 1959). 
The occurrences of two Coastal species, 
Parathemisto gracilipes and P. australis, and of 
the subtropical species, Hyperoche mediterranea 
Senna, are shown in Figure 4. Hyperoche 
mediterranea is restricted to a narrow range of 
temperature in the warmest waters (except for 
Station 100) whilst P. gracilipes and P. australis 
occur commonly over much the same salini- 
ties, but over a wider range of temperatures. 
