140 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



previous observations on the physiological harmony 

 subsisting between the tentacles, I was led to expect 

 that the co-ordination of the locomotor ganglia w^as 

 probably effected by means of the same tissue-tracts 

 through Avhich the intertentacular harmony was 

 effected, namely, those situated in the margin of the 

 bell. Accordingly, I introduced four short radial 

 cuts, one midway between each pair of adjacent 

 inariiinal bodies. The co-ordination, how^ever, was 

 not perceptibly impaired. I therefore continued 

 the radial cuts, and found that when these reached 

 one-half or two-thirds of the way up the sides of 

 the inner bell (or contractile sheet), the co-ordina- 

 tion became visibly affected, and this for the first 

 time. 



I also tried the following experiment. Instead 

 of beginning the radial cuts from the margin, I 

 began them from the apex of the cone ; and I found 

 that however many of such cuts I introduced, and 

 however far down the cone I carried them, so long 

 as I did not actually sever the margin, so long did 

 all the divisions of the bell continue to contract 

 simultaneously.* This fact, therefore, proves that 

 the marofin of the bell is alone sufficient to maintain 

 co-ordination, 



* This could be pnrticalarly well seen if, after the extreme 

 apex of the cone had been removed, one of the four radial cuts 

 was continued through the margin, and the latter was then 

 spread out into a linear form by gently pressing the animal against 

 the flat side of the glass vessel in which it was contained. The 

 same experiment performed on Aurelia is, of course, attended 

 with a totally different result, now one segment and now another 

 oiii^inating a discharge which then spreads to all the others in 

 the form of a contraction-wave. 



