THE ORIGIN OF NERVES. 



287 



ments, so as to form a mere elongated strip (Fig. 51), which 

 in its turn was intersected or divided by numerous slits 

 and notches, was still shown to transmit impressions, thus 

 proving that there was little selective choice by the im- 

 pressions of special lines or tracts along which to travel. 

 Mr. Romanes says of this experiment, that although the 

 swimming-bell of Aurelia had " been cut into the form of a 

 continuous parallelogram of tissue, and then subjected to 

 the tremendously severe form of section " (depicted in Fig. 

 51), "yet on very gently stimulating any point in this ex- 



;:'');) 1'. & {"S7 mm TTTT V- 



FIG. 51. Section of margin of the body of Aurelia (see Fig. 49). 



panse of tissue, as at the end a, a tentacular wave would 

 course all the way along the margin to b, thus showing that 

 the wave of stimulation must have passed round and round 

 the ends of all the intervening cuts." But in Tiaropsis we 

 see evidence of a higher development of sensitiveness and 

 nerve-action in the accurate response of the central mouth 

 to impressions made upon the swimming-bell. Here the 

 reception of impulses may be regarded as having become 

 specialised, and the influence of use and habit may be 

 credited with converting the at first ill-defined lines of 

 discharge into definite and accustomed tracts, along which 

 impulses would regularly and normally pass. In other 



