volves breathing, feeling, and smelling. But it has 

 another capacity also, and one which is of enormous 

 protective value to the animal: it enables it to 

 sense the deleterious presence of fresh- or brackish- 

 water. In short, this system is hydrostatic as well as 

 hydraulic. In passing, let me say that if further 

 proof were necessary that brackish-water is harm- 

 ful to the ophiuran, I need refer only to the fact 

 that within the preceding week four serpent-stars 

 were placed in my ordinary tanks with the result 

 that three died before two days had passed. The 

 remaining one was recovered before life became 

 extinct, by transferring it to its proper medium 

 here in the dark-room. 



Now it is that I notice a hazy cast seeming to 

 concentrate in the region of my lamp which has 

 remained stationary while I occupied myself with 

 the various reactions of the inmates. This haze is 

 of the most tenuous tint of blue, barely percep- 

 tible, and at the moment would probably not at- 

 tract my attention were I not anticipating some- 

 thing of the sort. It was in expectation of this that 

 my nocturnal visits were chiefly inspired. 



My statement that there were twelve serpent- 



[75] 



