DISPERSAL OF ROTIFERS 189 



Peak and the Pampas of La Plata ? . . . You have, no 

 doubt, long anticipated the solution of the puzzle, and see 

 clearly enough that living creatures to whom a yard of 

 sea water is as impassable a barrier as a thousand miles of 

 ocean, could only have reached or left Australia, New 

 Zealand, Jamaica, or Ceylon in the egg : not the soft 

 delicately-shelled and quickly-hatching summer egg, but 

 the ephippial egg, which is protected by a much harder 

 and thicker covering, constructed to bear without injury 

 a long absence from the water, and hatches, so far as is 

 known, some months after it has been laid. 



"... The case of the free swimming Kotifera is simple 

 enough. They are, most of them, to be found at some 

 time or another in small, shallow pools. . . . Such pools 

 frequently dry up, leaving the ephippial eggs. . . . Then 

 comes boisterous weather, and the dusty surface ... is 

 swept by the wind, which raises the dust high in the air, 

 ephippial eggs and all. For these latter are minute 

 things : few exceeding one-three-hundredth of an inch in 

 length, and many even half that size. Once raised in 

 the air, I see no reason why they should not be driven by 

 aerial currents unharmed half round the globe. 



" To this aerial carriage of the eggs is due the fact that 

 when any Eotifer is found in one spot, it is frequently 

 found at the same time in closely-neighbouring ponds 

 and ditches, even in such an unlikely hole as the print of 

 a cow's foot filled with rain, but not at all in more pro- 

 mising places at some distance off. 



"The eggs of the tube-makers (Fig. 61), however, and 

 of such Eotifers as live only in the clear water of lakes and 

 deep ponds, present a greater difficulty, for their eggs either 

 lie within their tubes or are attached to growing weeds, 

 or fall down to a bottom which lies covered all the year 

 round with several feet of water. The wind and sun 

 cannot be the only means of dispersion. Aquatic birds 



