PULMOGRADA.- 
KADIATA. CiLioGRADA. 397 
instance) out of the water, and lay it on a board or 
dry stone, it deliquesces so rapidly, that an individual 
weighing fifty ounces when taken out of the sea, has 
been found in no great length of time to leave nothing 
behind but a little dry cellular tissue weighing no more 
than five or six grains ! Their organs are arranged in 
ray-like processes radiating from a common centre or 
a longitudinal axis, in which are lodged the digestive 
organs. Their body is surrounded by a very delicate 
epidermis ; and on the arms, tentacles, and other parts 
of the body, there exist a number of cilia and peculiar 
prehensile organs, which produce when handled a 
stinging sensation like that of nettles. These are 
generally known by the name of nettling organs ; and 
it is from this stinging property that the Acalephshave 
acquired the name of Sea-nettles. 
These creatures are in general of small size, ordy 
rendered obvious, indeed, to the naked eye by another 
property they possess — that of their phosphorescent 
luminosity. Some, however, are of considerable dimen- 
sions, and as seen at night far out at sea, appear like 
globes of fire or cannon balls heated to incandescence, 
rolling along far below the keel of the ship. Some of 
them are hermaphrodite or bisexual, while others are 
of one sex alone. They are propagated by eggs, and 
according to the plan of what is known as the alter- 
nation of generations. The eggs produce a series of 
young which at first resemble infusory animalcules. 
These little creatures become fixed after a time, and 
assume a poh^p-like form, which gives birth bj^ gemma 
ation to a new progeny, which ultimately assumes the 
original form. They also multiply their kind by gem- 
mation alone, little ones springing out almost ready- 
made from the substance of their parents, chiefly from 
the walls of the peduncle, or the surface of the 
ovaries, and closely resembling the parent from which 
they sprung. 
The species of Acalephse are numerous ;* elegant 
pellucid beings, of varied hues, and diverse forms, float- 
ing on or near the surface of the water, and moving 
with a considerable variety of modes of locomotion. 
We arrange them in four orders, and this diversity 
in their method of progression forms an excellent basis 
for their classification. These four orders are — 
I. Pulmograda, or Discopliora, containing the 
Medusae, &c. 
II. Ciliograda, or Ctenophora, containing the Be- 
roes, &c. 
III. Cmdiigrada, containing the Velellae and Por- 
pitae, &c. 
IV. Phjsograda. containing the Physaliae and 
Diphyidae. 
Order L— PULMOGEADA or DISCOPHORA. 
The animals belonging to this order of Acalephae are 
♦ Some of the smaller kinds are very abundant in the northern 
seas. Scoresby (ells us that they are found chiefly in those por- 
tions oi the sea where the water was of an olive-green colour. 
The number, he says, was found to be immense. “ They were 
•about one-fourth of an inch asunder. In this proportion a cubic 
inch of water must contain 64; a cubic foot 110,592 ; a cubic 
fathom 23,887,882 ; and a cubic mile about 23,888,000,000,000 ! 
Provided the depth to which they extend be but 250 fathoms, 
the .above immense number of one species may occur in a space 
of two mites square.” 
generally known by the name of Medusae, “ Sea-blub- 
bers, or Jelly-fishes.” Their motion through the water 
is etfected by means of a powerful contraction of the 
body, b}' which the water contained in its hollow is 
expelled ; and by thus alternately dilating and contract- 
ing the body, the animals are enabled to propel them- 
selves with tolerable rapidity. 
The Medusae are entirely gelatinous, consisting of a 
large hemispherical disc, more or less convex above, 
very much like a mushroom or an umbrella. They 
have no solid axis, but have an elongated peduncle 
suspended from the inner surface of the umbrella, in 
which is situated a simple central stomach ; and the 
margin of the disc is furnished with long tentacula, 
which hang down from it in the water. The pellucid 
nature and hemispherical form of the Meduste have 
often caused them to be likened to glass globes and 
lamp glasses. 
The Pulmograde Acalephs or Medusae are divided 
into two groups or sub-orders : 1st. The Hooded- 
EYED Meduste or Phanerocarpae ; and 2nd. The 
Naked-eyed Medus.^e, or Cryptocarpae. 
To the first sub-order (Phanerocarpoi) belong the 
true Medusae, and these again have been divided into 
several families. 
The- family Rlnzostornidm is represented in Plate 2, 
fig. 4, by the species Rhizostoma Cuvierii, an inhabi- 
tant of the European seas. 
The famil}" Medusidce is represented in Plate 2, 
fig. 1, by the Medusa {Cyanea) aurita, a native of 
European seas ; in Plate 2, fig. 3, by the Pelagia pla- 
nospira. 
The second sub-order (the Cryptocarpce) or Naked- 
eyed Medusae contains numerous species. The British 
species have found an able historian in the late Profes- 
sor E. Forbes, who in his excellent memoir, published 
by the Ray Society, has described upwards of forty 
found on our shores. 
The family Geryoniidai is represented in Plate 2. 
fig. 6, by Geronyahexaphylla. 
The family Berenicidm is represented in Plate 2, 
fig. 5, b}' Berenice rosea. 
The family MUquoreidce is represented in Plate 1, fig. 
9, by the jPequorea Forslcaelina — a native of the Medi- 
terranean and Atlantic seas. 
Order II.— CILIOGRADA or CTENOPHORA. 
The animals belonging to this order of Acalephae 
are well represented by the curious creatures known 
by the name of Beroes. Their motion through the 
water is effected by means of numerous small vibratile 
cilia, disposed in rows upon the sides of the body. 
There are several families belonging to this order. 
The family Beroidm or True Beroes is represented in 
Plate 1, fig. 1, by the species Beroe macrostoma. 
The family Callianiridoe is represented by a species 
of Janira {J. hexagona), Plate 1, fig. 2. 
Genus Cestum. — This genus is an aberrant form of 
this order, but connected to the other members of it by 
a succession of intermediate links. It is represented in 
Plate 1. fig. 6, by the only species belonging to it, 
