ECOLOGICAL 57 



the aeronauts cannot direct their course and may be blown out to 

 sea. Thus Darwin records that when the Beagle was sixty miles from 

 land the rigging was covered one day with a multitude of little 

 spiders! We cannot expect these subtle adaptations to meet all 

 contingencies ; and even the apparent fatality of being blown far away 

 may lead, and indeed has led, to the peopling of high mountain- 

 plateaus and distant islands of the sea. 



When we think of long aerial journeys made by flightless animals, 

 made on the whole successfully, made with some measure of plas- 

 ticity, and more or less perfect on the first trial, we cannot but ask 

 how such a device could arise at all. As Goethe said: Animals are 

 always attempting the next to the impossible and achieving it; 

 and of this there is no better instance than the flight of gossamer- 

 spiders. By what inspiration did it begin? The general answer is 

 not very remote; the device is an outcome of the drag-line habit. 

 For it is almost a universal habit of spiders to pay out a drag-line 

 of silk when they are in any difficult or critical situation. A spider is 

 creeping back-downwards along the roof of our room, holding on by 

 its toothed claws to the roughnesses of the whitewash. If a flake 

 should give way under the tips of its toes the spider has 

 time to touch an intact spot with its posterior spinnerets. The 

 exuded silk adheres, a rope is instantaneously paid out, and down 

 this the spinner descends with dignity. There is a touch of perfec- 

 tion in the way it sometimes changes its mind, so to speak, when 

 half-way down, and proceeds to climb up its own rope, which dis- 

 appears as it climbs. This is finer than the Indian rope-trick, and 

 it actually occurs. 



Now it is from the drag-line habit, as Savory well shows, that 

 webs began, and the comfortable lining of the nest, the cocoon for 

 the hidden eggs, and the threads that make the silken parachutes 

 on which the spiders are buoyed through the air. Nowadays the 

 performance is instinctive, but it is quite reasonable to suppose 

 that each fresh inspiration was tested from age to age by individual 

 intelligence. Animals play for themselves, for better and for worse, 

 the hands of cards which they inherit ; and evolution is thus neither 

 magical nor fortuitous. 



ENCYSTATIONS. — Among the simplest organisms there are 

 many instances of encystation in face, not only of winter, but of 

 other difficulties. Thus the Amoebae may encyst in conditions of 

 drought, and it may be that the reduction of locomotor activity 

 and the secretion of a cyst can be interpreted as direct reactions 

 to the scarcity of water. The protection may be afforded almost 

 automatically. In the same group may be ranked the formation 

 of special "winter-eggs" in some small crustaceans, such as Daphnids. 

 They differ from "summer-eggs" in their more resistent shell and 



