KNOWLEDGE 



[Jan. 13, 1882. 



FOUND LINKS. 



Bv Dr. Andrew Wilson, F.L.S., ic. 



TURNING now to the la.st-named fi.shes {Lepidosiren 

 and Cei-aUxlim), wo di.scovcr tliat their tisli-characters 

 exist on the very surface of tliinj:;s. Their blood is cold ; 

 thfir bodies are .scaly ; they have fins and liii-rays; and 

 above all, they possess gills existing in tho sides of the 

 neck, and in which, so long as they swim in the water, 

 their blood is puritiod. IJut here the fish-characters end. 

 Another aspi-et of the niud-fislies and the barramunda 

 re\eals characters whidi startle us as lieing not those of 

 fishes, but those of frogs ; and frogs, toads, and newts 

 form, as every on<! knows, the second higher class of 

 vertebrate , that of the Amphibia. 



Firstly, dIici), the Lrpido/tiren possesses a heart, which 

 is not that of a fish, but modelled on the type of the frog 

 or reptile heart. Instead of being two-chambered, it 

 is throe-chambered ; and no other tish save itself pos- 

 sesses such an advance on the ordinary type of fish-heart. 

 But, secondly, their " paired fins," which represent in all 

 fishes the " limbs " of higher animals, resemble — in the 

 mud-fishes at least — rudimentary limbs. Then the nostrils, 

 thirdly, open into the mouth^a character agreeing with 

 frogs and all higher vertebrates, but possessed by one other 

 fish-group only — the low hag-fishes, which are poor relations 

 of the lampreys. Tliese characters, then, are the characters 

 of frogs, and not of fishes. But a far more interesting 

 likeness to the frogs and higher vertebrates yet remains 

 for notice. The " air bladder " of the mud-fisli and of the 

 " Jeevine " alters wonderfully, both in form and function, 

 from its nature in other fishes. It becomes divided in two, 

 and it opens into their throat by a windpipe, at the top of 

 wliich is a " glottis," corresponding to part of our own 

 organ of voice. Furthermore, it is divided internally into 

 cells — in a word, tho air-bladder of the mud-fish and its 

 neighbour Jtas heroine a Iuikj. But this wonderful trans- 

 formation is not quit<: ended with the recital of the altered 

 structure of the air-bladder in these fishes. A lung is an 

 organ which not merely receives blood in an impure state, 

 but which, as in ourselves, returns that blood pure to the 

 heart for re-circulation through the body. If, therefore, 

 the " lung " of the tish is to he accounted a true " lung," 

 we should be al)le to show that it performs the functions 

 and discharges the duties of an organ of lircathing. 



Now the life of these fishes exhil>its exactly the pecu- 

 liarities which demand the exercise of an air-breathing 

 organ like a lung. The mud-fishes iidiabit their native 

 rivers during the wet season ; but when the dry season 

 approaches, they bury themselves in the mud, and lie there, 

 baked as in a kind of mud-pie, until the return of the per- 

 sLstent rains. During this land-existence their " lungs " 

 come into play. So long as they live in their native 

 wat(!rs, they breatlie by their gills like ordinary fishes ; 

 but, ensconced in the mud, they breathe air directly 

 from the atmosphere, like ourselves. The air-bladder 

 purifies tho blood, which the heart pumps into its 

 ve-s-sels, and from the " lungs " the purified blood is 

 returned to the heart. Tho fish is thus truly a "double- 

 breather ; " it exhibits in itself the combination of the 

 characters of the frog and the fish. Dr. Giinther tells us 

 that whilst the mud-fi.shes remain in the "torpid state of 

 existence, the clay-l)alls containing them are frequently 

 dug out, .and, if the capsules are not broken, the fishes 

 imbedded in them can be transported to Europe, and re- 

 leased by being immersed in slightly tejnd water." The 

 " Jeevine," with its sirailar " luns;," is said to leave the 



Australian rivers at night, and to waddle its way to the 

 marshes and swamps, there to feed upon the vegetable 

 mattJ'rthat forms its .staple food. In the nocturnal joumey- 

 ings of the fish we can readily perceive the utility of the 

 "lung." 



It may lastly be remarked that other fishes are known 

 to leave tlie water and to exist for a time on land. The 

 climbing perch of India, and the Ophiorephali, also of 

 India, illustrate! such fishes ; but in these forms the 

 breathing in air is contrived in a different fashion from 

 that process in the mud-fishes, and has no connection with 

 any " lung." 



Let us now reflect that a frog itself begins life 

 as a fi.sh. Tlio "tadpole" has gills and a fish - heart, 

 whilst it lias no lungs. Ultimately it acquires lungs 

 and loses gills and tail as its mature shape is attained. 

 Summing up these plain facts of zoology, I think it 

 is not difficult to see that in the mud-fishes and " Jee- 

 \-ine " we find a " link " between the lower water-living 

 fishes and the air-breathing frogs. If we sup)iose that 

 a form like the mud-fish could rid itself of its gills when it 

 became adult, and that it could throw off the scales of the 

 fish, and develope the limbs of the frog, we might figure to 

 ourselves the ascent of the frog-typo from the Csh-type. 

 There is nothing more wonderful or impossible in this idea 

 than in the veritable fact that every frog is at first a fish, 

 then a tailed newt, and only ultimately becomes the 

 amphibian. Anyhow, one fact seems clear enough, that 

 fishes and frogs — two utterly distinct classes — are " linked " 

 by the mud-fishes and " Jeevine ; " and this single fact in 

 itself supports powerfully, in a rational view of matters, 

 the theory that the air-breathing tribes of animals sprang 

 originally from water-living forms. We shall see in future 

 papers that " links " even of stranger kind unite classes of 

 animals as dissimilar as the fishes and the frogs. 



FALLACIES ABOUT LUCK. 



Bv THE Editor. 



"TTTALKING down to the boat-houses, one day, when I 

 \* was at Cambridge, a friend (now a clergyman) 

 who was taking part, like myself, in the four-oared scratch 

 races, remarked that his boat w'as sure not to draw the 

 unlucky first place that clay. "How's thatT' I asked. 

 " Why, because we have had to row first every day until 

 now, and the luck is sure to change to-day." (It may be 

 necessary to explain that boat-races on the Cam are bump- 

 ing i-aces — unless where time races are i-owed between the 

 last two or three left in — and that the first place is, 

 of course, the worst in a bumping race, for the simple 

 reason that the first boat shares with the others, 

 all but the last, the risk of being bumped, but can- 

 not make a bump. In the eight-oared races, indeed, the 

 first place is the place of honour, attained by bumping 

 boats below ; but where, before a race, lots are drawn for 

 position, the first place is the worst, the last place the best) 

 I tried to explain to my friend what seemed so obvious as 

 to need no explanation, that his fate in the day's drawing 

 could not possibly be affected by the results of previcv.s 

 drawings. The simple circumstance that to draw a given 

 place day after day, for six days (fivo were pa-st), was a 

 thing unlieard of, so far as he knew, sufiiccd to assure him 

 that his coxswain would not that day draw a particular 

 ticket. It so chanced that what he was sure would not 

 happen did actually hajipen, though it would in no way 

 ha\e affected my argument if his hopes had lieen fulfilled. 



