FUNDAMENTAL EXPERIMENTS. 31 



amount of section it is possible to make upon any 

 of their parts other than their margins without 

 their spontaneity being in the smallest degree 

 affected. 



Effects of excising Certain Portions of the Margins 



of Nectocalyces. 



The next question which naturally presents itself 

 is as to whether the locomotor centres are equally 

 distributed all round the margin of a swimming 

 organ, or situated only, or chiefly, in the so-called 

 marofinal bodies. To take the case of the naked- 

 eyed Medusae first, it is evident that in most of the 

 genera, in consequence of the intertentacular spaces 

 being so small, it is impossible to cut out the 

 marginal bodies (which are situated at the bases of 

 the tentacles) without at the same time cutting out 

 the intervening portions of the margin. The genus 

 Sarsia, however, is admirably adapted (as a glance 

 at Fig. 1 will show) for trying the effects of remov- 

 ing the marginal bodies without injuring the rest 

 of the margin, and vice versa. The results of such 

 experiments upon members of this genus are as 

 follow. 



Whatever be the condition of the individual 

 operated upon as to freshness, vigour, etc., it endures 

 excision of three of its marginal bodies without 

 suffering any apparent detriment; but in most 

 cases, as soon as the last marginal body is cut out, 

 the animal falls to the bottom of the water quite 

 motionless. If the subject of the experiment 



