118 
DARWINISM 
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 ludovicianus, S. aurica- 
pillus, and S. noveboracensis) have taken many preliminary 
steps to becoming as aquatic as the dipper; and the winter- 
wren, and even the Maryland yellow-throat are not far 
behind.” 1 
Another curious example of the way in which species have 
been modified to occupy new places in nature, is afforded by 
the various animals which inhabit the water-vessels formed 
by the leaves of many epiphytal species of Bromelia. Fritz 
Muller has described a caddis-fly larva which lives among these 
leaves, and which has been modified in the pupa state in 
accordance with its surroundings. The pupae 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 swimming, 
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 which, both terrestrial and 
aquatic, also inhabit the bromelia leaves ; and as some water- 
beetles are known to frequent the sea, it is perhaps by these 
means that the first emigrants established themselves in this 
strange new abode. Bromelia) are often very abundant on trees 
growing 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. 
1 Nature, vol. xxx. p. 30. 
