34 
SCIENCE. 
Speculating on the ultimate conceptions of Matter which 
are affected by the discovery of it in “ a fourth condition,” 
Mr. Crookes says : “ From this point of view, then, Matter 
is but a “ mode of motion.’ ” 
It has never appeared to me that this well-known phrase 
is a very happy one, even as applied to Heat. It is possi- 
ble, of course, to consider Heat from this point of view. 
But then, it is equally possible to consider all other 
phenomena whatever from the same point of view. Not 
only Heat, but Light, Sound, Electricity, Galvanism, and 
Sensation itself in all its forms, may be regarded as 
“ modes of motion.” 
But at least in the application of this phrase to Heat 
there is an intelligible meaning, and not a mere confusion 
of thought. But as applied to Matter — as a definition of 
our ultimate conception of matter — it appears to me to 
confound distinctions which are primary and essential. 
“Motion” is an idea which presupposes Matter and 
Space. Motion has no meaning whatever except the 
movement of Matter in Space. To define Matter, there- 
fore, as a “ mode of motion,” is to define it as Matter in 
a state of motion. But this definition necessarily implies 
that Matter can also be conceived as without motion, and 
accordingly Mr. Crookes is obliged to confess that “ at the 
absolute zero of temperature inter-molecular movement 
would stop,” and that after that. Matter would remain with 
all the “ properties of inertia and of weight.” 
Again Mr. Crookes says : “ The space covered by the 
motion of molecules has no more right to be called Matter 
than the air traversed by a rifle bullet can be called lead.” 
No doubt this is true ; but it implies what is not true, that 
the common idea of Matter is nothing but “ the space cov- 
ered by the motion of molecules.” The popular idea at- 
tached to words of primary significance may not be always 
adequate or complete. But in my opinion they are gener- 
ally much more near the truth, and more accurately 
represent the truth than most of the phrases which scien- 
tists are now inventing in the region of transcendental 
physics. 
These phrases have their value and their interest as 
representing special and partial aspects of phenomena. 
But I hold that the unconscious metaphysics of human 
speech are often the deepest and truest interpretations of 
the ultimate facts of nature 
ON A NEW JELLY-FISH OF THE ORDER TRA- 
CHOMEDUSHL, LIVING IN FRESH WATER. 
On Thursday last, June to, Mr. Sowerby, the Secretary 
of the Botanical Society of London, observed in the tank in 
the water-lily house, in Regent’s Park a peculiar organism, 
of which he was kind enough to place a large number at 
my disposal on the following Monday. 
The organism proves to be an adult medusa belonging to 
the order Trachomedusx and the family Petasidx of Haec- 
kel’s system (“ System der Medusen,” Erster Theil). It 
comes nearest among described genera to Fritz Muller’s 
imperfectly known Aglauropsis from the coast of Brazil. 
The most obviously interesting matter about the form 
under notice is that it occurs in great abundance in per- 
fectly fresh water at a temperature of 90 0 Fahr. 
Hitherto no medusa of any order has been detected in 
fresh water — except perhaps some stray estuarine forms 
(Crambessa ?). 
It is exceedingly difficult to trace the introduction of this 
animal into the tank in the Regent’s Park, since no plants 
have been recently (within twelve months) added to the 
lily-house, and the water is run off every year. Probably a 
few specimens were last year or the year before present in 
the tank, and have only this year multiplied in sufficient 
abundance to attract attention. Clearly this medusa is a 
tropical species, since it flourishes in water of the high tem- 
perature of qo° Fahr. 
Mr. Sowerby has observed the medusa feeding on Daph- 
nia, which abounds in the water with it. 
The present form will have to be placed in a new genus, 
for which I propose the name Craspedacusta, in allusion to 
the relation of its otocysts to its velum. 
It is one of the sub-class Hydromedusae or Medusae cras- 
pedotae, and presents the common characters of the order 
Trachomedusae (as distinguished from the Narcomedusac) 
in having its genital sacs or gonads placed in the course of 
the radial canals. It agrees with all Tracholinx (Tracho- 
medusae and N.ircomedusx) in having endodermal otocysts, 
and it further exhibits the solid tentacles with cartilaginoid 
axis, the centripetal traveling of the tentacles, the tentacle 
rivets (Mantel-spangen), the thickened marginal ring to the 
disk (Nessel-ring) observed in many Tracholinae. 
Amongst Trachomedusx, Craspedacusta finds its place in 
the Petasidx, which are characterized as “ Trachomedusx 
with four radial canals, in the course of which the four 
gonads lie, with a long tubular stomach and no stomach- 
stalk.” 
Amongst Petasidx it is remarkable for the great number 
of its tentacles, which are all solid ; and for its very numer- 
ous otocysts. Further, it is remarkable among all Hydro- 
medusx (velate medusx, that is, exclusive of Charybdxa) 
for the fact that centrifugal radiating canals pass from the 
otocysts into the velum , where they end areally. 
The genus may be characterized as follows : 
Mouth quadrifid, with four per-radial lobes. 
Stomach long, quadrangular, and tubular, projecting a 
good deal below the disk. 
Disk, saucer-shaped, that is, flattened. 
Radiating Canals 4, opening into the marginal canal. 
Gonads 4, in the form of 4 oval sacs, depending into the 
cavity of the subumbrella from the four radiating canals. 
Marginal or Ring Canal voluminous. 
Centripetal Canals (such as those of Olindias, Gery- 
onia, etc.) absent. 
Tentacles solid ; in three sets, which are placed in three 
superimposed horizons : — 
1. A set nearest the aboral pole, of 4 large per-radial 
tentacles. These are the primary tentacles. 
2. A second tierof (in large specimens) 28 medium-sized 
tentacles placed between these in four groups of 
seven. These are the secondary tentacles. 
3. A third tier of (in large specimens) 192 small ten- 
tacles placed in groups of six between adjacent 
secondary tentacles. These are the tertiary ten- 
tacles. 
Tentacle-Rivets (Mantel-spangen) connecting the 
roots of the tentacles with the marginal ring (Nessel-ring) 
are connected with all the tentacles of each of the three 
horizons. 
Otoliths placed along the line of insertion of the velum 
— about eighty in number (fewer in small specimens). 
From sixteen to twenty are placed between successive per- 
radiai tentacles arranged in groups of two or three between 
the successive secondary tentacles. 
Velar Centrifugal Canals (which are really the 
elongated otocysts) are peculiar to this genus, passing from 
the otoliths (one inclosing each otolith) into the velum, and 
there ending blindly. They appear to correspond in char- 
acter to the centripetal canals found in other Trachomedusx 
in the disk. 
Ocelli are absent. 
[The presence of velar otocystic canals constitute the 
chief peculiarity of the genus Craspedacusta, and may 
necessitate the formation of a distinct family or sub order 
for its reception. The minute structure of the otoliths and 
canal-like otocysts I am now engaged in investigating.J 
The above characters are derived from the examination 
of adult male specimens, which were freely discharging 
ripe, actively motile spermatozoa. 
The species may be known as Craspedacusta Sowerbii, 
nov. gen. et sp. — I name the species in honor of Mr. Sow- 
erby, who discovered it, and to whose quick observation 
and courteous kindness zoologists are indebted for the 
knowledge of this interesting animal. 
The sole character which I can give as specific over and 
above the generic characters summarized above is that of 
size. The diameter of the disk does not exceed one-third 
of an inch. 
Locality. — The water-lily tank in the gardens of the Bo- 
tanical Society, Regent’s Park, London. 
Very abundant during June, 1880. Probably introduced 
from the West Indies. E. Ray Lankester. 
— Nature. 
