280 ON THE GENUS LUCERNARIA. 
but in which the radial canals still retain a very great width, 
and are separated from each other only by narrow dissepi- 
ments; which bud remains in this stage of development, 
reaches maturity, and develops sexual organs along the course 
of the radial canals. 
With respect to its Medusoid resemblance, I could here 
only repeat what has been laid down in many places in the 
former sections, and will merely add that, in the points where 
Lucernaria approaches the Meduse, it differs in the essential 
parts from the Actinioid animals. In it, for instance, we do 
find neither the stomach hanging in the visceral cavity, 
nor the reproductive organs seated on the free margins of the 
septa, both points characteristic of the Anthozoa. Nor have 
I been able to discern anything in its structure decidedly 
polypoid, as stated by Leuckart, who, according to his as 
yet unpublished researches, expresses a decided opinion in 
favour of the affinity between his Calycozoa and the polyps. 
The class Ceelenterata, which has everywhere met with the 
warmest acceptation, and against which Agassiz alone has ex- 
pressly declared himself, I would subdivide, as has also been 
done by Leuckart and others, into three sub-classes—Antho- 
zoa, Ctenophora, and Acalephe. 
These three divisions may be distinguished by the structure 
of the stomach; in Anthozoa it is suspended freely in the 
cavity of the body, which is divided into chambers by radial 
septa; in the Ctenophora, in which the construction of 
the stomach bears most resemblance to that of the Anthozoa, 
a canal system always exists, which conveys the products 
of digestion throughout the body, and in Acalephe the 
stomach either hangs freely down or is excavated in the sub- 
stance of the body itself. 'The Ctenophora, which are usually, 
since Escholtz, placed amongst the Acalephze, are so essen- 
tially separated from them by the microscopical structure of 
their parts, and have so much resemblance to the Anthozoa, 
that it is more proper to consider them as a group of the 
Ceelenterata, equivalent to the Acalephze and Anthozoa. 
Under the Acalephe I arrange, in the first place, the 
Meduse, with the hydroid polyps which have been properly 
grouped together as Hydrasmedusze ; and, as a second order, 
the Siphonophore. 'T'o the Hydrasmedusz, at first sight, 
belong very different creatures :—1, minute polyps, which 
split up into Medusze by the transverse division of their 
upper part; 2, large polypidoms, some of which throw off 
Medusa-like buds, while the propagation of others is carried 
on by ova; and 3 and lastly, Meduse, which have almost always 
originated as buds on polypes, though they are frequently 
