BIOPSYCHOLOGICAL 629 



well, and even in subtle cases where rapidity counts for much, as 

 when the male mosquito, automatically adjusting his antennae and 

 body like a living gyroscope, is able quickly to find the female 

 when she utters her shrill note, which is not to be confused with the 

 buzzing common to both sexes. 



Behaviour of Newly Hatched Loggerhead Turtle. — This 

 has been carefully studied by Howard and Parker, and may be 

 considered by itself, since it shows something a little different from 

 ordinary tropisms. Suddenly ushered into a new world, the little 

 creature hurries from its cradle in the sand to its future home in the 

 sea. It is constitutionally bound to go down a slope rather than up 

 (though it may climb if necessary), and it seems to be more influ- 

 enced by blue than by other colours — two inborn preferences that 

 may help it seawards — but careful experiment shows that its life- 

 saving reaction is to move away from the more blocked and inter- 

 rupted horizon and towards that which is open and free. It is 

 normally forced to go right, though the experimenter can force it 

 to go wrong. 



"The Dirigible Dog." — ^A well-known American inventor, Mr. John 

 Hays Hammond, made a very interesting light-driven machine that 

 is called "a dirigible dog". 



It moves on three wheels, two in front, which are geared to an 

 internal electric driving motor, and the third at the back, which 

 is the steering-wheel. On the very front are two 5-inch condensing 

 lenses, which appear much like large eyes. 



When these receive strong light-rays from an external source 

 they influence two cells composed of the element selenium, which is 

 remarkably sensitive to the effect of light. These selenium cells 

 control electro-magnetic switches which, in an intricate way, 

 regulate the current to the driving motor and also bring about the 

 turning of the steering-wheel. If a portable electric light, such as a 

 hand-torch, be held in front of the machine the queer contraption 

 immediately begins to move towards the light, and will follow it 

 round the room at a speed of about three feet a second. 



It is like a dog following a rabbit. If the electric torch light is 

 switched off the mechanical dog stops; or if the torch be quickly 

 moved to some distance the mechanism stops, like a dog that has 

 lost the scent. If the light be switched on again, or brought nearer, 

 the machine begins once more to move; if the light be all to one 

 side the machine moves to that side, and the turning will be such 

 as to bring the shaded selenium cell into the light. 



The principle of the machine has been used in connection with 

 a dirigible torpedo, and it perhaps throws some light on the turning 

 of the moth into the candle, for the moth seems to be automatically 

 seeking to get both its eyes equally illumined. At the same time we 



