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PACIFIC SCIENCE, Vol. XV, October 1961 
FIG. 1. Ventral side of Velella killed and fixed in process of eating three large and three smaller fish eggs. 
Smaller eggs, marked by vertical lines, have diameter of 1.1 mm. Gastrozooid surrounding central egg has 
broken and appears as thin film above egg. Darkest egg is not completely ingested. 
the volume of a euphausiid egg. This means 
that in the Velella taken in March of 1954, fish 
eggs almost equalled the volume of euphausiid 
eggs in the diet of Velella, while in the May 
1950 sample fish eggs were 120 times the vol- 
ume of euphausiid eggs. The ventral side of a 
Velella taken in the process of eating six fish 
eggs is shown in Figure 1. 
When the Velella were collected in March 
1954, a surface net tow was taken at the same 
time. In Table 1 the per cent composition of 
the plankton is compared to the per cent com- 
position of the food of Velella. Euphausiid 
metanauplii and copepods were 10 times as 
common in the plankton as in Velella food. On 
the other hand, euphausiid eggs were nearly 8 
times as common in the food of Velella as in 
the surface zooplankton. Larvaceans, which 
made up 10 per cent of the food by count, 
formed less than 0.1 per cent of the plankton. 
If the plankton sample is representative of the 
food that was available to this particular Velella 
population (change with time or micro-vertical 
distribution differences may mean the plankton 
sample is not representative), it appears that 
motile organisms such as copepods and nauplii 
are not caught as effectively as are weaker swim- 
ming zooplankton, such as the larvaceans or the 
nonmotile eggs of fish and invertebrates. Never- 
theless, comparatively large and active organ- 
isms such as larval fish and adult euphausiids 
are occasionally caught. 
In Figure 2 the per cent composition by 
count of the food of the 99 specimens taken 
in May 1950 is shown as a function of mean 
length of Velella. Apparently there is no marked 
food selection by the different sizes of Velella 
although the calanoid copepods (3) increase 
steadily in importance when Velella surpasses 
a length of 30 mm. This is another indication 
that motile organisms are not caught as effec- 
tively as are nonmotile objects. Besides jack 
mackerel eggs and the items listed in Table 1, 
the following items were found in the gono- 
