Nutrition among the Hydromedusce. 179 
movement could be easily distinguished; and I should infal¬ 
libly have remarked an aperture if there had been one. 
It is therefore an undoubted fact that among the individuals 
of Bougainvillea paradoxa there are some which have no 
buccal aperture, no communication between the exterior water 
and the gastrovascular system of the Medusa—a fact which 
appears to me very curious, and furnishing no explanation 
how the nutrition and growth of the organism can be effected. 
The fact is the stranger because these anomalies are observed, 
and indeed most frequently, in Medusae which are but very 
little exceeded in size by the normal adult individuals. They 
must consequently have been able to grow and to nourish 
themselves, since from microscopic embryos they have attained 
a size of more than half a centimetre. 
Besides Bougainvillea paradoxa we find in the White Sea 
another Medusa belonging to the same genus, but distinguished 
from the former by the general form of the body (PI. XX. 
fig. 6 ), which is more elegant, with a little cupola placed on 
the summit of the bell, and further by the possession of eight 
instead of four black ocelli, by the presence of three tentacles 
(never more) in each of the four groups, and, lastly, by the 
very short and sparingly ramified buccal tentacles. This 
Medusa occurs less frequently than the other; and it is also 
of rather smaller size. 
As in the former species, although less frequently, I have 
met with individuals which differed from the normal type in 
having nothing coloured about them except the eight black 
ocelli, and no red coloration in the centre—that is to say, where 
the coloured manubrium ought to be situated. The cause was 
the same, namely the total deficiency of the manubrium 
(PI. XX. fig. 7) and of the buccal orifice. As may be seen 
from the figure, the four radial canals unite without forming 
a stomachal cavity ; and by examining the animal under the 
microscope the complete absence of any orifice, aperture, or 
pore by which the sea-water with its nutritive contents might 
penetrate into the canals is easily ascertained. 
It may therefore be proved that, at least in two different 
species, the Medusa may live, increase in size, and develop 
itself without having any need of digestive organs, and even, 
apparently, without nourishment, since the latter cannot pene¬ 
trate into the gastrovascular system. One cannot help asking 
how all these functions can be performed, how the Medusa 
can grow and become a complete Medusa from an almost im¬ 
perceptible embryo, without the aid of organs of nutrition and 
without food. The supposition that all this can take place 
without nourishment is absurd and cannot be accepted ; it is 
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