48 THE ELEMENTARY NERVOUS SYSTEM 



stance by cutting, is inflicted on a finger of Stylotella, it 

 will, if not too far away, call forth a temporary contrac- 

 tion of the osculum. This does not occur commonly when 

 the injury is two centimeters from the osculum, but it does 

 occur with great regularity when the injury is within one 

 centimeter of that aperture. What it is that is transmitted 

 from the seat of injury to the contractile tissue about the 

 osculum is by no means clear. That it is not due to escap- 

 ing juices from the wound has already been shown. It 

 may be brought about by a slow progressive contraction 

 of the flesh which, starting at the wound, gradually creeps 

 to the sphincter, or it may be a slow progressive transmis- 

 sion unaccompanied with any real contraction. Such a 

 transmission as that first mentioned would be in the na- 

 ture of a progressive muscular wave whereas that last 

 suggested would partake of the essentials of a sluggish 

 nervous transmission. Which of these two methods oc- 

 curs in Stylotella cannot at present be stated, but that 

 there is in many tissues a sluggish transmission unac- 

 companied with observable motion and, therefore, nerve- 

 like is beyond question. Such neuroid transmission, lim- 

 ited in the extent over which it may spread, is in all prob- 

 ability to be attributed to sponges. It is in all likelihood 

 the form of transmission characteristic of the continuous 

 protoplasm of such forms as the protozoans. This trans- 

 mitting capacity is so undifferentiated and so limited in 

 its power to spread that while it may be looked upon 

 as the germ from which nervous transmission has grown, 

 it cannot be said to be a sign of nervous tissue. In con- 

 sequence of the absence of effective transmission in 

 sponges the various effector elements of these organisms 

 lack coordination almost completely. Thus, as already 

 stated, the closure of one osculum through the local ap- 



