34 



SCIENCE. 



Speculating on the ultimate conceptions of Matter which 

 are affected by the discover)' 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- 

 CHOMEDUSzE, LIVING IN FRESH WATER. 



On Thursday last, June 10, 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 Trachome.lusae and the family Petasidae of Haec- 

 kel's system (" System der Medusen," Erster Theil). It 

 comes nearest among described genera to Fritz Miiller'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 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 0! <)fJ 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 llydromedusa: or Medusae cras- 

 pedotx, and presents the common characters of the order 



Trachomedusae (as distinguished from the Narcomedusae) 

 in having its genital sacs or gonads placed in the course of 

 the radial canals. It agrees with all Tracholinae (Tracho- 

 medusae and Narcomedusae) 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 Trachomedusse, Craspedacusta finds its place in 

 the Petasidae, which are characterized as " Trachomedusse 

 with four radial canals, in the course of which the four 

 gonads lie, with a long tubular stomach and no stomach- 

 stalk." 



Amongst Petasidae 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- 

 medusae (velate medusae, that is, exclusive of Charybdaea) 

 for the fact that centrifugal radiating canals pass from the 

 otocysts into the velum, where they end ccccally. 



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) 2S 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- 

 radial 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 Trachomedusae 

 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 suborder 

 for its reception. The minute structure of the otoliths and 

 canal-like otocysts I am now engaged in investigating.] 



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 Sowermi, 

 nov. gen. ct 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 docs 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. 





