190 



FRESHWATER FAUNA 



and dogs are probably assisting agents. The birds as 

 they swim among the water-plants must frequently set 

 free the eggs from the tubes of the Ehizota, as well as 

 those which adhere to Confervse, Potamogatons, and 

 water-lilies, and so get them attached to their feathers. 

 Then away they fly, carrying the 

 eggs to some far-off lake, or shak- 

 ing them into the air with the 

 flapping of their wings. 



"In confirmation of this idea, 

 I may mention that the well- 

 known naturalist, Mr. John Hood, 

 of Dundee, informs me that the 

 Scotch lakes most prolific in new 

 and rare species are those which 

 are annually visited by wild fowl 

 from the North." 



I have given this quotation at 

 some length, since it admirably 

 states and meets the difficulties 

 presented by the problem of dis- 

 persal, and its explanations are 

 not restricted to the case of the 

 Eotifers, but will be found to 

 apply to the other classes of 

 organisms w 7 hich multiply by 

 means of winter eggs. 



No doubt many of the minute 

 Crustacea are disseminated by the 

 wind as well as by birds ; some 

 of them resemble the Eotifers in the production of two 

 kinds of eggs. 



The water-fleas, Daphnia, and its family afford an 

 excellent illustration of this ; development proceeds 

 within the egg, and the young are hatched out fully 



FIG. 61. A Tube-making 

 Rotifer (Floscularia lon- 

 gicaudata, Hudson). After 

 Hudson and Gosse. 

 Magnified about 100 

 diameters. 



