2 ACCOUNT OF THEIR STRUCTURE. 
by far the most prolific in results; the voyages which I had the pleasure of making with my 
friend Mr. M‘Andrew around the British coasts having afforded admirable opportunities for 
the study of our Medusee. These creatures are of so very delicate and often unpreservable 
a nature, that casual circumstances usually determined the extent to which the examination of 
their structure and habits could be pursued, and as most of my observations had necessarily 
to be made at sea, those circumstances were not always most favorable. In the present 
very unsatisfactory state of this branch of zoology, however, I do not think it necessary to 
apologise for unavoidable imperfections, for having often experienced the difficulty of con- 
ducting inquiries into tribes of which the species had as yet been but vaguely defined and 
rarely figured. I trust this account of an important and beautiful tribe of animals, of which so 
far as the British seas are concerned, only a few very fragmentary notices are accessible, may 
serve as a basis for future and more extensive researches. They offer a fresh and but little 
explored field for discovery. Their organization is but partially understood, and much requires 
to be done before the signification of their several parts be fully made out; of their habits 
we possess but very slight knowledge. Their development is a subject of the greatest interest, 
seeing that upon its clearing up will probably depend the future classification of the zoophytes. 
On most of these points I can scarcely pretend to speak; what I offer are the rudiments only 
of an extensive subject. It is for naturalists expert in physiological and anatomical investi- 
gations, skilled in the use of the microscope, and not too trustful in its revelations, free in 
their movements, and with time untrammelled at their disposal, to carry out this most interesting 
branch of research, to which, if my imperfect monograph give an impetus, 1 am content— 
Quod potui, fect; quod restat suppleat alter 
Doctior, et nostris faveat non invidus ausis. 
Before commencing a detached description of the species, it is best to examine the 
features of organization common to the tribe. 
The parts presented by these animals are the following : 
A. The disk or umbrella. This forms the greater portion of the animal’s body. It is 
hemispheric, but varies from being extremely depressed and almost plane, as in certain species 
of Thaumantias and Aiquorea, to a nearly cylindrical form, as in Zurris. One of its commonest 
shapes is that of a round glass shade, such as is placed over ornaments or statuettes to 
protect them from dust. It is usually smooth, rarely pilose. Its under surface, on which in 
certain tribes the reproductive bodies are placed, is called the sub-umbrella. Around its 
margin internally there is in many species a projecting ledge of membrane called the vedl 
(velum). The margin itself is usually provided with more or less numerous tentacles (eirrz 
marginales), of variable structure, the bases of which are often swollen into a bulb, and 
deeply coloured or marked with a brilliant spot (oced/us). In the substance of the disk are 
the vessels, often conspicuously visible. 
B. From the centre of the sub-umbrella hangs a more or less produced proboscis-like 
body (pedunculus), of variable form and dimensions. In this is the stomach, and, in certain 
genera, the ovaries. At its extremity is the mouth, surrounded by variously-formed contractile 
lips, occasionally furnished with produced tentacula. 
Such are the characters visible at a glance. A more minute examination makes us 
acquainted with the structures they include. 
