§ Short Papers and Notes. 
The Fellv-Fish. 
One of the most notable cases of the curious development 
amongst the jelly-fishes is illustrated by the history of one of the 
commonest members of the race—the Aurelia aurita, whose title 
to be called the ‘common jelly-fish” can hardly be disputed. 
From the egg of this organism is first developed a little oval, free- 
swimming speck named the /lanula. Attaching itself to some 
fixed object, the planula assumes a pear-shaped form, and, as a 
depression at its free end deepens to form a mouth, little tentacles 
bud out around the opening. In such a guise—exactly resembling 
the hydra of our fresh-water pools, or the primitive bud of a 
zoophyte—does the progeny of the Aurelian jelly-fish appear; and 
when the tentacles have become numerous it receives the name of 
fTydra tuba—a term applied, under the belief that it was a dis- 
tinct form of animal life, by Sir J. G. Dalyell, the once-famous 
authority on zoophyte life and structure. In length the Hydra 
duba organism measures about half-an-inch, and, curiously enough, 
it has been known to continue in this stage of development for 
years. It, moreover, possesses a power of producing other //ydra 
tube by a process of budding, and thus comes to imitate perfectly 
the conditions of zoophyte existence. Its further history begins 
when the body elongates, and when it becomes marked across by 
grooves or indentations, which gradually deepen, whilst their 
edges become notched. In this stage Sars named the organism 
Scyphistoma, believing it to be a new and mature animal. As the 
f1ydra tuba becomes further divided cross-wise, it assumes the 
appearance aptly described as a pile of saucers with notched edges 
placed one within the other, their hollows being turned upwards. 
Now it is known as the S¢rodi/a. Sooner or later: this pile of 
saucer-like bodies—each called an “fp/hyra—falls to pieces; the 
saucers each swim freely in the water; they assume a more 
concave form, and appear before the observer as veritable jelly- 
fishes, or Aurelzz, which pulsate through the sea, and which 
exhibit all the characteristics of their species and race. Not the 
least surprising fact in connection with this curious life-history is 
that which informs us of the extreme disparity between the size of 
the “ydra tuba and of the beings to which it may thus give 
origin. A //ydra tuba measuring about halfan-inch long breaks 
up into saucer-hke £phyra, or jelly-fishes, each of which latter, 
when fully developed, may measure seven feet in diameter and 
may possess tentacles fifty feet long. Huge oceanic jelly-fishes, 
occurring in tropical seas, and measuring from six to eight feet 
across, thus spring from a fixed organism whose diminutive size 
would seem to preclude the possibility of its containing even 
potentially the energies requisite for the development of an 
ordinary-sized jelly-fish. Such facts are not unparalleled in higher 
life-histories. ‘The germ of the sperm whale is a mere microscopic 
