118 DARWIKISM chap. 



several seconds, a large part of the body is submerged. Now 

 these birds still have the plumage pervious to water, and so 

 are liable to be drenched and sodden ; but they have also the 

 faculty of giving these drenched feathers such a good shaking 

 that flight is practicable a moment after leaving the water. 

 Certainly the water- thrushes (Seiurus ludo\acianus, S. aurica- 

 pillus, and S. noveboracensis) have taken many preliminary 

 steps to becoming as ac^uatic as the dipper ; and the Avinter- 

 wren, and even the Maryland yellow-throat are not far 

 behind." ' 



Another curious example of the way in which species have 

 been modified to occupy new places in natiu-e, is afforded by 

 the various animals which inhabit the water- vessels formed 

 by the leaves of many epiphytal species of Bromelia. Fritz 

 Miiller has described a caddis-fly larva which lives among these 

 leaves, and Avhich has been modified in the pupa state in 

 accordance with its surroundings. The jmpce of caddis-flies 

 inhabiting streams have fringes of hair on the tarsi to enable 

 them to reach the surface on leaving their cases. But in the 

 species inhabiting bromelia leaves there is no need for s'vnmming, 

 and accordingly we find the tarsi entirely bare. In the same 

 plants are found curious little Entomostraca, very abundant 

 there but found nowhere else. These form a new genus, but 

 are most nearly allied to Cythere, a marine type. It is believed 

 that the transmission of this species from one tree to another 

 must be effected by the young Crustacea, which are very 

 minute, clinging to beetles, many of Avhich, both terrestrial and 

 aquatic, also inhabit the bromelia leaves ; and as some water- 

 beetles are kno'wii to frequent the sea, it is perhaps by these 

 means that the first emigrants established themselves in this 

 strange new abode. Bromelise are often very abundant on trees 

 gromng on the water's edge, and this would facilitate the tran- 

 sition from a marine to an arboreal habitat. Fritz Miiller has 

 also found, among the bromelia leaves, a small frog bearing- 

 its eggs on its back, and having some other peculiarities of 

 structure. Several beautiful little aquatic plants of the genus 

 Utricularia or bladder-wort also inhabit bromelia leaves; and 

 these send runners out to neighbouring plants and thus spread 

 themselves Avith great rapidity. 



^ Nature, vol. xxx. p. 30. 



