408 EVENINGS AT THE MICROSCOPE 



yet more, on the repeated contractions of the corrugating 

 walls of the body. Occasionally, the free extremity of a 

 filament would appear, but more frequently the bight of 

 a bent one, and very often I saw two, and even three, issue 

 from the same cinclis. The successive contractions of the 

 animal under irritation caused the acontia already pro- 

 truded to lengthen with each fresh impetus, the bights 

 still streaming out in long loops, till perhaps the free end 

 would be liberated, and it would be a loop no longer; and 

 sometimes a new thread would shoot from a cinclis, whence 

 one or two long ones were stretching already; while, as 

 often, the newcomers would force open new cinclides for 

 themselves. The suddenness and explosive force with 

 which they burst out appeared to indicate a resistance 

 which was at length overcome perhaps (in part at least) 

 due to the epithelial film above mentioned, or to an actual 

 epiderm, which, though often ruptured, has ever, with the 

 aptitude to heal common to these lowly structures, the 

 power of quickly uniting again. 



"It appeared to me manifest from this and other similar 

 observations that no such arrangement exists as that which 

 I had fancied: that a definite cinclis is assigned to a 

 definite acontium, or pair of acontia; and that the extrem- 

 ity of the latter is guided to the former, with unerring 

 accuracy, by some internal mechanism, whenever the exer- 

 cise of the defensive faculty is desired. What I judge 

 to be the true state of the case Is as follows: The acontia^ 

 fastened by one end to the septa or their mesenteries, lie, 

 while at rest, irregularly coiled up along the narrow inter- 

 septal fossae. The outer walls of these fossas are pierced 

 with the cinclides. When the animal is irritated, it imme- 

 diately contracts: the water contained in the visceral cavity 



