INVESTIGATION ON THE FUNCTION OF REISSNER'S FIBRE. 569 



material showed that the fibre liad been broken) the animal was found 

 to retire to the darkest part of the tank and there to remain sluggishly 

 with head and tail sharply uplifted, and often with the body sharply 

 l3ent or in a sinuous curve. In the rays, the whole body was often 

 strongly arched transversely as well. The reaction lasted for a longer 

 or shorter period, and was usually very pronounced. 



Subsequently, in the aquarium, specimens were found showing this 

 reaction, and the examination by sections of their central nervous 

 system showed that in each case Eeissner's fibre had been broken in 

 life, presumaljly by some recent accident. 



Thus the principal result of the breaking of Ileissner's fibre in the 

 living animal appears to be that the animal adopts, while at rest, an 

 unnatural pose, and probably also swims with a slightly difi'erent 

 action. This lends support to the suggestion put forward by Dendy 

 iXi'turr. December. 1909), that the apparatus forms part of a mecha- 

 nism for automarically regulating fiexure of the body. 



