CO-ORDINATION. 141 



The next experiment I tried was to make four 

 short radial incisions in the margin as before 

 described, and then to continue one of these in- 

 cisions the Avhole way up the bell. By careful 

 observation I could now perceive that all the 

 marginal ganglia did not discharge simultane- 

 ously ; for when those situated nearest to the long 

 radial cut happened to take the initiative, the 

 resulting contraction- wave, having double the dis- 

 tance to travel which it would have had if the long 

 radial cut had been absent, could now be followed 

 by the eye in its very rapid course round the bell. 

 Now, the fact that in this form of section I was 

 able to detect the passage of a wave, proves that 

 the three short radial sections had destroyed the 

 co-ordinated action of the marginal ganglia. 



From these experiments, then, I conclude that in 

 this genus ganglionic co-ordination, in the strict 

 sense of the term, is effected exclusively by means 

 of the marginal nerves. And as these experiment*^ 

 on Sarsia are exceedingly difficult to conduct, owing 

 to the very rapid passage of contraction-waves in 

 this genus, it is satisfactory to find that this con- 

 clusion is further supported by the analogy which 

 the other species of naked-eyed Medusre afford, and 

 to the consideration of which we shall now proceed. 



The effects of four short radial incisions through 

 the margin of any species of Tiaropsis, Thaumantias, 

 Staurophora, etc., are usuall}^ very conspicuous. 

 Each of the quadrants included between two adjacent 

 incisions shows a strong tendency to assume an 

 independent action of its own. This tendency is 



