SIDE I.IGHTS ON BIRDS 



they have come to this pass that they can reckon 

 up their pedigree and race." 



In many quadrupeds, too, the evolution of 

 movement may be traced. The common rat is 

 not normally aquatic ; the presumption is that it 

 shares with other thin-skinned and sensitive 

 creatures of its type a distaste for water as a 

 bathing medium. Yet when the pressure of 

 circumstances forces it to live in a sewer it becomes 

 an expert swimmer and diver. 



Perhaps the most striking example of natural 

 movement changed by new conditions is seen in 

 the pointer and setter. Something of a rudi- 

 mentary " point " may be noted in the fox and 

 other animals which approach their prey by 

 stealth. In the fox it is a mere instinctive pause 

 in order that the exact position of the crouching 

 rabbit may be determined before the fatal pounce 

 is made. In the pointer and setter this pause is 

 prolonged by training ; the momentary check is 

 extended indefinitely. To watch a highly- 

 trained dog strike a hot scent is a curious and 

 instructive sight. It is seen to be the subject of 

 two opposing currents of emotion ; the one 

 urging it forward to leap upon and tear its prey, 

 the other holding it back as with an iron hand. 

 The raised foot and the spasmodic working of the 

 jaw mark the strong internal conflict. 



Movements of Birds under Water. 



The movements of different species of birds 

 when pursuing their prey under water are, of 

 necessity, not always easy to trace. Some idea 

 of their relative methods may be gathered from 

 an examination of the structure of the birds 

 themselves. 



To take the cormorants first, the black and the 

 green, we note at once that the legs and webbed 



48 



