50 
PACIFIC SCIENCE, Vol. XIII, January 1959 
5,6). On the other hand, it has been remarked 
that Coastal species have not penetrated into 
water of subantarctic origin. A possible ex- 
planation of these facts is that some cold- 
adapted Subantarctic species can survive the 
increase in temperatures between cold sub- 
antarctic and warm coastal waters, but that 
coastal species are unable to adapt to lower 
temperatures. It is difficult to see that this 
explanation is totally adequate. A preponder- 
ant one-way movement of Subantarctic spe- 
cies into coastal areas is demonstrated in the 
T-S-P diagram (Fig. 10), and is also apparent 
from analysis of the plankton catches at sta- 
tions of Series 4 for example (Figs. 17, 18). 
When oceanic waters move into coastal wa- 
ter, compensatory movements out of the area 
should ensue. At least some of the low- 
density inshore water might escape by over- 
riding denser subantarctic water, in which 
case coastal species would be carried offshore 
and their numbers gradually decrease as en- 
vironmental conditions become adversely 
modified. The opposite appears to be true in 
most instances. The numbers of the Coastal 
group of species captured decrease abruptly 
between 12.5 and 13.0°C. (Fig. 9), as the 
oceanic water is reached, e.g., as at Stations 
285, 297, Series 4. It seems unreasonable to 
suppose that the abruptly effected absence of 
the Coastal species results from a sudden ap- 
plication of some physiological factor, and it 
is suggested that there may be reasons in- 
volving hydrological phenomena. 
It is possible that the northeast moving 
current along the coast sets up a superficial 
transverse circulation (Sverdrup et al., 1942: 
676-677) which passes surface oceanic water 
shorewards. It is conceivable that offshore, 
surface transport of organisms could be pre- 
vented by the development of such a circula- 
tion. This mechanism would tend to accumu- 
late less dense water to the left of the direction 
of flow, i.e., along the coast. In turn, this 
would facilitate a lateral, offshore transfer of 
water, and the contained organisms, at deeper 
horizons. Flowever, such would not be re- 
vealed by the surface sampling of this survey. 
A second possibility is that the transfer 
between the coastal and subantarctic waters 
proceeds through the agency of discrete 
pockets of water, formed on a small scale but 
in an analogous manner, to those between 
the Gulf Stream and neighboring waters 
(Iselin and Fuglister, 1948; Ford and Miller, 
1952). Isoline configurations in several of the 
Figures 11-20 suggest the development of 
pockets on the shoreward side of the north - 
going oceanic waters. If the transfer of surface 
water were largely shorewards, as seems possi- 
ble, it would assist in explaining the abrupt 
cessation of the offshore occurrences of 
Coastal species. 
The method of the T-S-P diagram is suit- 
able for determining the tolerances of species 
to temperature and salinity in that it demon- 
strates their reactions to changes in environ- 
mental conditions. The fact that data are 
collected in the field is advantageous and 
especially so when considered in conjunction 
with experimental evidence, for example of 
the long or short term temperature adapta- 
bility of species. Sheard (1953: 21, and per- 
sonal communication) indicates that temper- 
ature tolerances may vary according to the 
range to which the local stock of a species has 
become adapted; the occurrences of Thysa- 
noessa gregaria in the present survey appear to 
be a case in point. In general, Th. gregaria is 
rarely captured in subantarctic waters (Sheard, 
1953; Boden, 1954). But it was consistently 
taken as a Southern Subantarctic species dur- 
ing the present survey. It reacted to increasing 
temperatures (Fig. 6) by a reduction in num- 
bers in a manner similar to other species of 
the Southern Subantarctic Group. It is possi- 
ble that this may be a stock of Th. gregaria 
which is adapted to cold water. If so, con- 
siderable interest would accrue at this stage in 
comparing upper and lower temperature tol- 
erances of this and Subtropical stocks, both 
by experiments and through field data by 
means of the T-S-P diagram. 
The technique of the T-S-P diagram has 
