354 THE ZOOLOGIST. 



field naturalists on these points tends to prove how partial or 

 moderate must be the danger in the present day, and how con- 

 siderably more intense it must have been in some former time 

 to have prompted the evolution of the wonderfully simulating 

 guises, which we can only conceive as evolved for protective 

 purposes. 



A repetition of observations will frequently qualify the pre- 

 mises on which many conclusions are based. Many recorded facts 

 are of course utterly erroneous. Thus in 1666 Schefferus records 

 in the 'Philosophical Transactions ' that Swallows sink into lakes 

 in autumn, and hibernate in a manner precisely similar to Frogs. 

 In 1741 Fermier-General Witkowski made legal testimony to the 

 effect that two Swallows had been taken from a pond at Didlacken 

 in his presence in a torpid state ; that they eventually regained 

 animation, and after fluttering about, died some three hours after 

 their capture. In 1748 the great Swedish chemist Wallerius 

 wrote that he had on several occasions seen Swallows clustering 

 on a reed until they all disappeared beneath the surface.* Thus 

 a traveller in a tropical forest might from paucity of observation 

 form a wrong impression as to the relation of the liane and the 

 stem or tree to which it is attached. He would frequently find 

 " the hard basal parts of a liane stem twisted and coiled appar- 

 ently around nothing. This is due to the fact that the original 

 support had been killed, and then, slowly rotting into dust, has 

 been denuded away by the wind and rain." Our traveller might 

 then record the murderous action of lianes as of a somewhat 

 universal character. But further observations would show the 

 action quite reversed. As Kerner describes the process : " If 

 the erect young stem is stronger and more vigorous than the 

 twiner which encircles it, which has been used as a prop, it does 

 not allow itself to be strangled ; the twiner is destroyed when 

 they both increase in thickness. The coils of the climber are 

 gradually stretched tighter and tighter, and many are the contri- 

 vances which exist for preventing the tension from immediately 

 acting injuriously on the movement of the sap in the interior of 

 the twining liane stem. As this thickening continues, the pull 

 on the coils becomes so great that the death of the liane results."! 



* Cf. Dixon, ' The Migration of Birds,' 2nd edit. p. 54. 

 f Kerner and Oliver, ' Nat. Hist. Plants,' vol. i. p. 682. 



