54 ANATOMY AND PHYSIOLOGY OF SALPA AND PYROSOMA 



and a more beautiful sight can hard!}' be imagined than that presented 

 from the declvs of the ship as she drifted, hour after hour, through this 

 shoal of miniature pillars of fire gleaming out of the dark sea, with an 

 ever-waning, ever-brightening, soft bluish light, as far as the eye could 

 reach on every side. The Pyrosoniata floated deep, and it was with 

 difficulty that some were procured for examination and placed in a 

 bucketful of sea-water. The phosphorescence was intermittent, 

 periods of darkness alternating with periods of brilliancy. The light 

 commenced in one spot, apparentl}' on the body of one of the 

 "zooids," and gradually spread from this as a centre in all directions; 

 then the whole was lighted up ; it remained brilliant for a few seconds, 

 and then graduall}- faded and died awa}', until the whole mass was 

 dark again. Friction at any point induces the light at that point, and 

 from thence the phosphorescence spreads over the whole, while the 

 creature is quite freshly taken ; afterwards, the illumination arising 

 from friction is only local. 



43. So far as could be observed the Pyrosoina had no power of 

 locomotion ; any such power arising from a contraction of the hollow 

 cylinder is out of the question, as its substance is cartilaginous and 

 non-contractile. Any one who does not examine these animals quite 

 closely may be readily deceived on this point ; for the alternate fading 

 and brightening of the phosphorescent light gives rise to the impres- 

 sion that the creature recedes from and approaches the ej^e ; and 

 viewing them from the deck of a ship only, it is difficult to imagine 

 that they do not really mo\'e with some rapidity.^ 



44. The Pyrosoina may be described as a hollow cylinder, solid and 

 hard to the touch, closed and rounded at one end, open at the other. 

 A narrow lip projects inwards at the open extremity ; it has been 

 called a membranous diaphragm, but in the specimen examined it 

 was certainly cartilaginous and immovable, like the rest of the animal. 

 The thickness of the wall of the cylinder was about two-fifths of an 

 inch; its diameter was about one inch and a half; its length was 

 about 10 inches. The outer surface of the cylinder was covered 

 with a multitude of small projections, and close to them opened 

 small circular apertures. The inner surface of the cylinder was 

 uneven but not rough, and was similarly pierced with circular 

 apertures. 



The wall of the cylinder consists of a vast number of minute 



' My observations upon the power of locomotion of Pyrosoina were very imperfect, as I 

 was anxious rather to attend to the more interesting points of structure. Certainly the 

 cylinder does not contract as a whole, but it is very possible that the zooids do, and so move 

 by the reaction of the forced-out water against the closed end of the cylinder. 



