Marvels of the Universe 



501 



long periods of suspension. As an adaptation to these we find that the Water Fleas are extremely 

 prolific, able to reproduce very rapidlj- while conditions remain favourable, while their eggs are well 

 able to withstand desiccation, and may be blown about in the dust without any diminution of 

 vitalitj-. As soon as rain comes, and they find themselves in a puddle, they hatch, and a new 

 period of rapid growth and reproduction sets in until the next interruption. It is in this way 

 that their presence so soon after rain in even the smallest and most temporary pools is to be 

 accounted for. 



On the approach of winter Daphnia produces another kind of egg, enclosed in a hard-shelled, 

 puxse-hke sheath. These, instead of developing rapidly like the summer eggs, remain ifoating in 

 their sheaths throughout the winter, and do not hatch until the following spring. 



The Water Fleas are b}' no means confined to fresh water, but exist in vastly greater variety in 

 the sea, where thej- sometimes assume most fantastic forms. A peculiarity common to those that 

 frequent the open ocean is the enormous development of spines and hairs, which are of service in 

 keeping the animal suspended in the water, on the same principle that a feather or dandelion seed 

 floats in the air. 



Small and delicate though these creatures are, geological evidence of their existence in 

 long-past ages of the world's history is by no means wanting ; indeed, the very rocks that 

 contain the bones of the gigantic reptiles about which we have already learned in these 

 pages contain also beds in which the tiny shells of contemporaneous Cyprids are crowded 

 together in vast quantities, proving that Cypris abounded in the shallow lakes and marshy 

 pools of those days even as it does in similar situations to-daj-. 



[.?. L Bastin. 



LIGHT AND THE PLANT. 



The Eucalyptus is typical of plants that grov*- in places where the heat of the sun is intense. The effect of its scorching 

 rays would tend to dry up the leaf, and these, for this reason, hang downwards and so escape the danger. 



