ON THE GENUS LUCERNARIA. 281 
also developed directly from ova. All these forms, however, 
are closely allied, as the numerous transitions between them 
show; and however great may be the importance set by 
nature in the higher animals, on the processes of reproduc- 
tion and development, this seems to be by no means the case 
in the order of creatures we are considering ; and however 
regularly the different stages of ovum, polyp, and Medusa, 
may, in one form, be gone through, in another this regularity 
is entirely wanting, and the animal often remains at the 
polyp stage, and whilst in it becomes capable of repro- 
duction; often also it entirely omits the polyp stage, and 
emerges at once from the ovum in the form of a Medusa. 
But all these diversities, as has been said, afford no ground 
for systematic divisions, and since we find the Medusoid 
generation to be subdivided into two forms, which were dis- 
tinguished as far back as by Escholtz, and have been named 
by Gegenbaur, the Acraspeda and Craspedota, so also can the 
Hydrasmedusze in the same manner be divided into sub- 
orders, to which the Lucernariadz are to be associated as a 
third. 
When we thus assign Lucernaria as a sub-order to the 
order of the multiform Hydrasmeduse, all that is extra- 
ordinary in its structure by degrees disappears. Since in this 
order we find numerous Medusz originating immediately 
from the ovum, and others which first bud out into a poly- 
pidom, it is readily conceivable that there may also exist 
forms exactly as in Lucernaria, in which the Medusa remains 
at the commencement of its development, but is capable, in 
this conditiou, of reaching sexual maturity. 
8. The genus Lucernaria and its species—Having thus 
considered the structure and systematic position of Lucer- 
naria, we may define the genus as follows : 
Lucernaria, O. F. Miller, 1776. 
An animal presenting the general structure of a Medusa, 
having the form of a pedunculated bell. The peduncle dilated 
at the base into a discoid expansion, by which the animal at- 
taches itself. The margin of the bell produced into eight more 
or less projecting arms, furnished with numerous tentacles, 
and which arms are often arranged in four pairs. Four wide 
radial canals, separated only by thin dissepiments, and com- 
municating with each other at the border of the bell. Mouth 
elongated into a quadrilateral oral tube. Internal tentacles 
in the stomach. Sexual organs situated in eight tracts in 
