478 
PACIFIC SCIENCE, Vol. XXI, October 1967 
food, hydrostatic pressure, and bio-physico- 
chemical interrelations with other organisms 
of the pelagic realm. Also to be considered is 
the structure of the population, since young 
individuals appeared to be at levels closer to 
the surface than were adults (Alvarino 1964a, 
1965*). 
SIPHONOPHORAE 
A greater number of species was observed 
in the upper 100 m in the daylight series than 
in the night (Figs. 3 and 4). The species ob- 
served in the upper 100 m for both series were 
Muggiaea atlantica, Chelophyes appendiculata, 
and Eudoxoides spiralis. These were joined in 
daylight by Eudoxia russelli, Lens id hotspur , 
L. subtiloides, Amphicaryon acaule, and Steph- 
anomia bijuga, and only by A. ernes ti, L. multi- 
cristata (extending also to the mesoplanktonic 
levels), and Nectodroma reticulata at night. 
The last two inhabited the mesoplanktonic 
domain in daylight. 
The daylight haul from 460 to 0 m was in- 
cluded in the diagrams for the siphonophores 
only, to show the presence of several species 
at those levels. However, the bathymetric 
limits cannot be determined for some species; 
thus, the upper limit of the daylight distribu- 
tion for Chuniphyes moserae, Ch. problematica, 
and Heteropyramis maculata , and both upper 
and lower limits for L. challengeri and Necto- 
droma dubia, are not yet established. 
The mesoplanktonic species appeared in 
higher numbers at night than in daylight. 
Typical mesoplanktonic species such as L. ajax, 
L. conoidea, L. grimaldii, Bargmannia elon- 
gata, Stephanomia rubra, Physophora hydro- 
statica, and N. dubia were not observed at 
night; and Nectopyramis diomedeae, N. thetis, 
and N. natans were not observed in daylight. 
Species appearing in the mesoplanktonic levels 
at night which extend to deeper layers at day- 
light were L. achilles, Vogtia kuruae, and 
Rosacea p lie at a. Dimophyes arctica was ob- 
tained in the mesoplanktonic levels at night 
and only at the bathyplanktonic zone during 
daylight. 
Species occupying both meso- and bathy- 
pelagic regions were Ch. multidentata, Ch. 
moserae, Ch. problematica, Clausophyes galeata, 
Crystallophyes amigdalina, Heteropyramis 
maculata, L. achilles, L. hostile, L. lelouveteau, 
L. reticulata, and Nectodroma reticulata (in 
daylight) . 
Species observed at the bathyplanktonic 
levels only were Clausophyes ovata, Ceratocymba 
dentata, and L. havock. 
One specimen of Velella (longest axis 70 
mm, and sail oriented NW-SE) was obtained 
with a dip net, 8 September 1965. 
One complete colony of Physophora hydro- 
statica was obtained in daylight at depths of 
350-250 m. 
MEDUSAE 
Higher numbers of species were observed 
during the night series than in the daytime 
(Figs. 5 and 6). Liriope tetraphylla was the 
only species found for both series in the upper 
100 m, presenting a higher number during 
daylight. Sibogita geometric a and Cunina pere- 
grina were observed only at night and in the 
upper 100 m. Phialidium discoidum and Cros- 
sota alba were observed during daylight in 
these upper strata, and extended from 685 to 
1030 m at night. 
The mesoplanktonic species were Sarsia coc- 
cometra, Zanclea costata, Pandea violacea, 
Heterotiara anonima, Colobonema sericeum, 
Cross ota alba, C. brunnea (extending deeper 
at night), and C. pedunculata. 
Species populating both the meso- and 
bathypelagic levels were Halicreas papillosum, 
Atolla wyvillei, and Periphylla hyacinthina (ob- 
served only at night). 
Medusae observed exclusively at the deepest 
levels were Homeonema alba, Aegina citrea, 
and Nausithoe rubra. 
The medusae showed some degree of stratifi- 
cation related to the size of the specimens; 
thus individuals of A. wyvillei 12-30 mm in 
diameter appeared at 300-235 m, whereas 
specimens 75 mm in diameter were found at 
1710-1450 m. However, specimens up to 100 
mm in diameter were obtained in the 620-530 
m level. The size-stratifications for this species 
appeared to be more clear-cut during the day- 
light series, when individuals 7-20 mm in 
diameter appeared in the 460-410 m level, and 
those 30-60 mm in diameter at 1720-1340 m. 
