JELLYFISH. 77
obtained magnificent strobilae by its means. Chrysaora is a
stable and hardy form and in a large sink strobilated every
year; the colour of the strobila (deep brown mahogany to
faint pink) depended entirely upon the degree of light present
at the situation in which strobilation took place.
All the remaining Aurelia forms and the two Cyaneas required
different or additional foods in order to strobilate; Miss Renton's
form refused all artificial food save the clitellum of garden
worm, and since these Hydra Tubae are almost invisible—so
small are they—their feeding was no light task, but it was
successfully accomplished. Normally Rentoni preys on Copepods,
and consumes "silt."
Types 1 and 3 and the Cyaneus strobilated on a mixed diet
of worm and chopped liver of Littorina rudis, but Type 4 would
not strobilate until fed on small nereids. All this was in addition
to natural food in the aquaria and jars: Type 1 used to capture
and consume post-larval whelks (B. undatum). No Hydra Tuba
of Aurelia refused semi-rotten and liquid Nereis if offered.
The strobilae varied, of course, in number of ephyrae according
to the species and to the size of the Hydra Tuba strobilating.
Aurelia Type 2 frequently produced 25 to 30 ephyrae in a
strobila, whilst other Aurelia types were content with four or
eight in a strobila or even, as with the third type, three only.
Chrysaora produced from one to three only and Cyanea from
four to eight per strobila.
It may be asked "Why does he not say what these creatures
are like in appearance?" The fact is, this is by no means an
easy task if one is to be exact in one's description. Generally
the wine glass supplies the best conventional description, the
bowl, the stem, and the basal disc. In addition, the bowl should
be covered over and a fairly pronounced tube should arise in the
centre. At the periphery of the bowl at least sixteen extremely
long and delicate tentacles should be imagined and also just
above the stem a stouter sort of tentacle, one only, should
be postulated, which is used chiefly for budding. But, unfortu-
nately for the investigator, he is dealing with one of the most
adaptable and protean creatures imaginable, and once he has
commenced to feed his stock he will find that they will shortly
change out of recognition, in most cases, and keep on changing,
even in the one individual. In the very young stages all Hydra