200 



♦ KNOWLEDGE ♦ 



[Sept. 5, 1884. 



been known as a receiver of small insects and crustaceans, 

 and it has been known as an insect feeder for at least 

 twenty years. Mrs. Treat, of America, in 1875 gave a 

 full and interesting description of the habits of one species 

 {Utricularia clandestina), and Darwin and others, of 

 Europe, studied the habits of other species in Europe and 

 elsewhere. 



In its character as an insectivorous plant the bladder- 

 wort might fail to arouse general iuterest, but as a des- 

 troyer of carp it has a commercial as well as botanical and 

 scientific character. The common bladder-wort {Utricularia 

 vulgaris) affords the easiest subject for study, inasmuch as 

 its bladders reach the largest size and may be satisfactorily 

 examined with a moderate magnifier. 



The bladder is pear-shaped, with an opening at the small 

 end. Around the mouth are anteniue like projections or 

 bristles, which, according to Darwin, are for the purpose of 

 warding off and keeping out insects of too great size. The 

 mouth is closed hy a valve which yields readily to light 

 pressvire, but offers an immovable barrier to the once 

 captured creature. The utmost strength compatible with 

 such a structure has apparently been attained. The valve 

 is a thin and transparent plate, and, by means of the water 

 behind it, is made to stand out a bright spot, which 

 Darwin thinks may attract prey. Something certainly 

 attracts the tiny denizens of the water, for they swim up 

 to the mouth and crawl into the bladder by the readily 

 yielding door. As there is no seductive seci-etion here, as 

 in the case of many insect-destroying plants, the great 

 naturalist's surmise is probably correct. 



Some of the insectivorous plants, on catching their prey, 

 at once pour out a digestive fluid analogous to the gastric 

 juice of the human stomach, but with the Utricularia it is 

 not so. The insects or other food when caught in the 

 bladder are merely captives, and swim about in their con- 

 fined quarters with eager activity in their endeavour to 

 find an outlet, until asphyxia for lack of oxygen comes on. 

 Even now the plant makes no effort to digest the animal 

 food, but waits patiently until decay takes place, and the 

 animal matter is by putrefaction resolved into fluids which 

 the numerous papilla; lining the bladder can absorb. 



Darwin's experiments showed not only that living 

 animals could make their way into the bladder, but that 

 inanimate objects falling on the valve would be engulphed 

 with lightning-like rajjidity. With all this information to 

 begin with, it is not strange that naturalists should turn to 

 the bladder-wort to seek a solution for the great destruction 

 of the carp, for the carnivorous plant was known to possess 

 facilities not only for the capture of floating spawn, but 

 even of tjie newly hatched fish. Examination and repeated 

 experiment proved conclusively that the greedy little 

 bladders were making sad havoc with the fish, and in con- 

 sequence carp breeders are bidden to open war vigorously 

 on Utricularia and all its species. It may seem at a hasty 

 glance that the small bladders can hardly be responsible 

 for any very extensive destruction of eggs or small fish, 

 but the doubters of the ability of insignificant agents, 

 acting together, to produce stupendous effects may be 

 referred to the microscopic rhizopods or the earth worms, 

 each in their own way performing vvonderful feats in the 

 way of earth building and earth preserving. — Scientijic 

 American. 



Catalpa Ties. — The catalpa ia already in use in the south-west 

 of the United States, to some extent, for railwaj' ties. It is a wood 

 of rapid growth, and yet has shown lemarkablo durability. In 

 an address before an agricultural society in Ohio, General 

 Harrison, of Indiana, mentioned a catalpa foot-log over a small 

 stream in the Wabash county which had been in use for 100 

 years, and was still sound, showing no aign of decay. 



OTHER WORLDS THAN OURS. 



A WEEK'S CONVERSATION ON THE PLURALITY OF 



WORLDS. 



By Mons. de Fontenelle. 



with notes by eichard a, peoctoe. 



THE SECOND EVENING {continued). 



" T FIND," says the Marchioness, "the planets are just 



X like us ; we cast that upon others which Ls in our- 

 selves. The Earth says, ' 'Tis not I that turn, 'tis the 

 Sun ; ' the Moon says, ' 'Tis not I that shake, 'tis the 

 Earth ; ' the world is full of error." 



" But I would not advise you," said I, " to undertake 

 the reforming it ; you had better convince yourself of the 

 entire resemblance of the earth and the moon. Imagine, 

 then, these two great bowls suspended in the heavens. Yon 

 know that the sun always enlightens the one half of a body 

 that is round, and the other half is in the shadow. There 

 is, then, one half of the earth, and one half of the moon, 

 which is enlightened by the sun — that is, one half which 

 is day, and the other half which is night. Observe, also, 

 that as a ball has less force after it has been struck against 

 a wall, and rebounds to the other side, so light is weakened 

 when it is reflected. The pale light which comes to us 

 from the moon is the very light of the sun ; but it cannot 

 come to us from the moon but by reflection. It has lost much 

 of the force and lustre it had when it came directly from the 

 sun upon the moon ; and that bright light which shines 

 directly upon us from the sun, and which the earth reflects 

 upon the moon, is as pale and weak when it arrives there, 

 so that the light which appears to us in the moon, and 

 which enlightens our nights, is the part of the moon which 

 has day ; and that jiart of the earth which has day, when 

 it is opposite to the part of the moon which has night, 

 gives light to it. All depends upon this, how the moon 

 and the earth behold one another. At the beginning of 

 the month we do not see the moon, because she is between 

 the sun and us ; that half of her which has day is then 

 turned toward the sun, and that half which has night 

 is turned towards us ; we cannot see it then, because it has 

 no light upon it : but that half of the moon which has 

 night, being turned to the half of the earth which has day, 

 sees us without being perceived ; and we then appear to 

 them just as the full moon does to us. So that, as I may 

 say, the people of the moon Lave then a full earth ; but 

 the moon being advanced upon her circle of a month, comes 

 from under the sun, and begins to turn towards us a little 

 corner of the half which is light ; which is the crescent : 

 then those parts of the moon which have night, do not see 

 all that half of the earth which has day, and we are then 

 in the wain to them."* 



"I comprehend you very well," said the lady; "the 

 people in the moon have a month quite contrary to us ; 

 when we have a full moon, their half of the moon which 

 is light, is turned to our half of the earth which is dark ; 

 they do not see us at all ; and they have then a new earth, 

 this is plain. But now tell me how come the eclipses 1 " 



" You may easily guess that," said I ; " when it is 

 new moon she is between the sun and us, and all her dark 

 half is turned towards us who have light, that obscure 

 shadow is cast upon us ; if the moon be directly under the 

 sun, that shadow hides him from us, and at the same time 

 obscures a part of that half of the earth which is light ; 

 this is seen by that half of the moon which is dark : here 



* Fontenelle omits to notice here the varying aspect of the eart\> 

 to the moon, as rotation turns different parts of her surface moon- 

 wards. But he touches on this point in the next chapter. — K. P. 



