SECTION OF COVER ED- EYED MEDUSAE. 77 



sage of a wave of stimulation, is a siglit as beautiful 

 as it is unique ; and it affords a first-rate oppor- 

 tunity of settling tlds all-important (question, namely, 

 Will this conductile or nervous function prove 

 itself as tolerant towards a section of the tissue as 

 the contractile or muscular function has already 

 proved itself to be ? For, if so, we shall gain nothing 

 on the side of simplicity by assuming that the 

 contract ^on-^yilveii are merely muscle- waves, so long 

 as the conduction or unclouhfcclly nervous waves 

 are equal 1}^ able to pass round sections interposed 

 in their path. Briefly, then, I find that the nervous 

 waves of stimulation are quite as able to pass round 

 these interposed sections as are the waves of con- 

 traction. Thus, for instance, in this specimen (Fig. 

 12), the tentacular wave of stimulation continued 

 to pass as before, even after I had submitted the 

 parallelogram of tissue to the tremendously severe 

 form of section which is represented in the illustra- 

 tion; and this fact, in my opinion, is one of the most 

 important that has been brought to light in the whole 

 range of invertebrate physiology. For what does it 

 prove ? It proves that the distinguishing function 

 of nerve, where it first appears upon the scene of 

 life, admits of being performed vicariously to almost 

 any extent by all parts of the same tissue-mass. If 

 we revert to our old illustration of the muslin as 

 representing the nerve-plexus, it is clear that, how- 

 ever much we choose to cut the sheet of muslin with 

 such radial or spiral sections as are represented in 

 the illustrations, one could alwa^'s trace the threads 

 of the muslin with a needle round and round the 



