566 
TILE RHIZOSTOMA, 
Lest any of my readers should become fellow-sufferers with myself, I advise them to be 
very careful when bathing after a strong south-west wind has prevailed, and if ever they see a 
tawny mass of membranes 
and fibres floating along, to 
retreat at once, and wait 
until it is at least a hundred 
yards away. Some may 
suppose that this advice is 
needlessly timid, but those 
who have once felt a single 
poison thread across their 
hand or foot, will recognize 
that discretion is by far the 
wisest part to be played 
whenever there is the least 
danger of being stung by 
the Cyansea. 
The last family, of 
which a small specimen is 
represented in the accom- 
panying illustration, is 
easily known by the 
absence of a mouth. In 
the typical genus, Rhizos- 
toma, the footstalk is 
deeply scooped into semi- 
lunar orifices, and the eight 
cartilaginous arms are 
without fringes. 
Before taking a final leave of these remarkable beings, it is needful that we should 
briefly notice the strange metamorphosis through which some of them pass before they assume 
their well-known form. Experiments were made on a species of Chrysaora, by Sir John 
Dalyell , with the following result : — When first sent into the world, the young Medusae were 
little flat, worm-like creatures, too minute to be examined by any except the highest powers 
of the microscope. By degrees, these tiny beings settle down to one spot and affix themselves, 
the body lengthens, arms begin to be shown, and after a while the strange creature is developed 
into the being known as the Hydra tuba. 
Satisfied, apparently, with its condition, the Hydra remains in the same spot for some 
time, and produces a number of young Hydras, which sprout like buds from its sides, and, 
when separated, resemble their parent. Here, we might naturally imagine to be the end of its 
history, for, with almost all animals, when a being is able to produce young, it is considered 
as having attained the utmost development of which it is capable. The Hydra, however, has 
yet other phases through which to pass. Towards spring, its body becomes much lengthened 
and wrinkled, so as to form a number of folds, just as if a series of threads had been tied 
tightly round it, one below the other. The upper rings now rapidly expand and the folds 
deepen, until the animal resembles a number of saucers regularly increasing in size, laid 
upon each other. The edges of each saucer are developed into two-cleft rays, and in this 
condition the animal proves to be the beautiful zoophyte discovered by M. Sars, and called 
the Strobila. 
These are, indeed, strange vicissitudes in life, changes more marvellous than even those 
wrought by water and magic words, in the old days when Haroun Alraschid ruled the faithful. 
There is yet more to come. The uppermost and largest disc or saucer now lengthens its rays 
RHIZOSTOM A Bhizostoma cuvieri. 
