274 MOVEMENT 



Scorpions move very rapidly ; their progression is 

 due to a series of sudden springs, which can be pro- 

 voked by excitation. The sequence of movements is 

 so swift that we have found it impossible to determine 

 their nature by means of photography (Fig. 195). 



All these insects moved about on glass covered with 

 paper or transparent muslin, and were viewed by 

 translucent or reflected light. Their movements were 

 directed by means of two sheets of glass, which were 

 arranged so as to be parallel and vertical, and thus to 

 prevent them from leaving the desired track. These 

 few examples will suffice to show how to collect and 

 compare from various species of animals chrono- 

 photographs of different types of locomotion. In a 

 collection of a great number of photographs of this 

 kind one will find the necessary elements for the 

 study of comparative physiology, a study which we 

 mean to pursue. 



