1 6 THE PSYCHIC LIFE 



peduncles. These are filaments capable of rolling 

 themselves up into the form of a cork-screw, when the 

 animal is disturbed. Certain Infusoria can modify 

 the form of their body by a sudden contraction: they 

 have been called metabolic; such are the Stentors, 

 the Prorodons, the Spirostomes. In contradistinction, 

 those which do not change their form, for example the 

 Paramecia, have been called ametabolic. Accord- 

 ing to the observations of Lieberkiihn, which date 

 back to 1857, the metabolic Infusoria have their 

 bodies divided into large granulous bands, separated 

 by bright filaments. It has been asked which is the 

 contractile element: is it the band, or is it the fila- 

 ment? Oscar Schmidt, Kolliker, Stein, and Rouget 

 think that it is the band which is the contractile ele- 

 ment. This opinion is based on the following fact, 

 which M. Rouget was the first to observe: at the mo- 

 ment at which the animal contracts, the band presents 

 transverse striae; this appearance is due to the fact 

 that the bands contain in the state of rest small gran- 

 ules which, during the contraction of the animal, are 

 disposed in transverse series, so as to recall the sar- 

 cous elements of Bowman. 



Lieberkiihn, Greef, and Engelmann attribute the 

 active part to the bright fibre. Engelmann has based his 

 opinion on the fact that he recognized in the filament 

 the property of double refraction, which, according to 

 him, belongs to all contractile substances, while the 

 substance which separates the filaments shows only 

 single refraction. 



However that may be, it is one of these two ele- 

 ments that possesses the power of contraction, and 

 which deserves the name of myophane, which Haeckel 

 gave it. It is very remarkable that in the Stentors 



