NEUROID TRANSMISSION 75 



ming plates is quite subordinate to that through which 

 their normal activity is called forth and which in all re- 

 spects agrees with the type of neuroid transmission al- 

 ready described in ordinary ciliated epithelia. 



Prom these examples it appears that the ordinary tis- 

 sues of animals, at least their ciliated epithelia, may ex- 

 hibit sluggish forms of transmission that are so like those 

 seen in sponges as to admit of being classed under the 

 single head of neuroid transmission. Such a form of 

 transmission is represented in sponges not only by the 

 closure of their oscular sphincters when a more distant 

 part of the animal is injured, but by their system of flag- 

 ellated cells whose activity, like that of the cells in a cili- 

 ated epithelium, must be coordinated by some such form 

 of transmission. Although of the three identifiable ele- 

 ments of the neuromuscular mechanisms of animals, 

 sense organs, central nervous organs, and muscles, 

 sponges possess only muscles, they nevertheless exhibit 

 among their many activities neuroid transmission, a slug- 

 gish form of transmission that may be considered the 

 forerunner of nervous activities, and in this sense may 

 represent the germ from which has sprung the real nerv- 

 ous conduction of the more complex animals. 



