Central Pacific Salpidae — Yount 
123 
listed salps and other zooplankters by station 
and numerical frequency. Such a comparison 
is made more reliable by the fact that Russell 
and Colman used a 1-meter coarse interna- 
tional silk townet, which has an approximate 
mesh width of 0.42 mm.; the 1-meter nets 
used by POFI have a mesh width of 0.65 
mm. (King and Demond, 1953). In addition, 
Russell and Colman towed their nets ob- 
liquely at each station for approximately a 
half hour, as was done for the POFI col- 
lections. 
The chief difficulties with such a compari- 
son are: (1) the amount of water strained was 
not computed by Russell and Colman and 
thus estimates of relative abundance of the 
plankton are only approximate; (2) volumes 
of the different groups of plankters were not 
determined for the Great Barrier Reef col- 
lections and thus, number of organisms, a 
relatively poor measure, offers the only means 
of comparison; and (3) the depth to which 
the POFI tows were made was approximately 
200 meters, whereas those of the Great Bar- 
rier Reef Expedition were made to approxi- 
mately 30 meters. 
Russell and Colman (1935) listed the tuni- 
cates which occurred in oblique tows with 
the 1 -meter coarse silk townet by species, 
reproductive form, and numerical frequency 
at 59 stations of the Great Barrier Reef lagoon. 
Comparison of these data with the data from 
the central Pacific reveals some striking differ- 
ences. Only 6 salp species (4 with the coarse 
silk townet) were captured in the Barrier Reef 
lagoon, whereas 19 (16 on cruises 5 and 8) 
were captured in the central Pacific. Thalia 
democratic a was by far the most numerous and 
frequently occurring species (80,987 speci- 
mens at 39 Barrier Reef stations), as it also 
was in the central Pacific. The fact, however, 
that T, democratica was lacking from fully 20 
of the 59 Barrier Reef stations is surprising 
when compared with the POFI collections, 
where it was absent at only 2 out of 81 stations 
examined. In addition, this species was occa- 
sionally much more numerous in the Barrier 
Reef lagoon than in the central Pacific (maxi- 
mum numbers at one station of 17,000 and 
3,440, respectively). 
The other species found in the Great Bar- 
rier Reef lagoon rank among the relatively 
less common and infrequently occurring spe- 
cies in the central Pacific: Brooksia rostrata 
occurred in the Barrier Reef at 10 stations out 
of 59 (117 specimens), whereas in the POFI 
collections, it occurred at 24 stations out of 
81 (259 specimens); 111 specimens of Pegea 
confoederata occurred at 8 stations out of 59 
in the Barrier Reef, whereas 185 specimens 
occurred at 12 stations out of 81 in the central 
Pacific; Weelia cylindrica occurred at 13 sta- 
tions (53 specimens) out of 59 from the Great 
Barrier Reef, whereas it occurred at 23 stations 
out of the 81 POFI collections examined 
(259 specimens). With the exception of T. 
democratica , the most numerous and fre- 
quently occurring species in the POFI col- 
lections, Salpa fusiform is, Ritteriella amhoinensis , 
Cyclosalpa pinnata , and Traustedtia multitenta- 
culata , did not occur at all in the Great Barrier 
Reef collections. All of these species, how- 
ever, occur in oceanic Australian waters 
(Thompson, 1948). 
Another striking difference between the 
collections from the Great Barrier Reef and 
those from the central Pacific is the large 
number of stations from the former at which 
no salps occurred (15 out of the 59 listed), 
whereas in the POFI collections, salps oc- 
curred at all 81 stations examined. In addition 
to the 59 tunicate-containing stations listed 
by Russell and Colman, there were 9 other 
collections made, which contained no tuni- 
cates. 
On examining their data, another difference 
becomes evident; that is, a maximum of 
17,003 specimens of salps (almost all T. demo- 
cratica) was captured at one station, whereas 
the maximum number at any one station in 
the POFI collections was 3,864 (chiefly T. 
democratica). The maximum number of salp 
species taken with the coarse silk townet at 
any one station in the Great Barrier Reef, 
