104 DK. WEBB, ON THE NOCTILUCA MILIARIS. 



arger membranous sac. The external layer distended by 

 degrees till it suddenly burst. I should mention that a new 

 supply of water had been given before most of these changes 

 happened. I have also been successful in separating the two 

 layers mechanically, by means of pressure slowly and steadily 

 applied to the animal under the screw compressor. The whole 

 internal network of fibrous tissue, with the manner in which 

 it invests the so-called " vacuoles," is most beautifully demon- 

 strated by the effect of iodine. The creature dies suddenly 

 without collapsing. The progress of the fluid can be traced 

 along the fibres into the minutest meshes ; and there remains 

 for a long time a transparent ball, traversed in every direction 

 by the brown fibres, beaded with the vacuoles and granules, 

 and having every reticulation on the surface sharply defined. 

 I am inclined to regard the tentacle as tubular, with an 

 orifice on the inner side at its base. At any rate, I have seen 

 the colour, when iodine has been used, proceed slowly towards 

 the distal extremity ; and under the influence of indigo poi- 

 soning, the granular matter of which the striation consists, 

 has been disarranged, scattered up and down the interior of 

 the organ, and in the end has aggregated together in small 

 globules without much impairing the power of motion. I 

 recognize no trace of striation in the external membrane ; and 

 when seen in the normal condition by transmitted light, there 

 is always a clear substance surrounding the dark centre. This 

 gives the impression of being made up of a series of discs or 

 rings. The tentacle is extremely brittle, and breaks with a short 

 fracture. I have never perceived any tendency to restoration 

 of the lost pai't, nor any independent movement in the de- 

 tached fragment. The stump continues active, and readily 

 comes off at the base. The point is a little flattened. When 

 the animal is killed in such a manner that this organ has free 

 play, it always shows a disposition to coil up spirally. The 

 cilium may be found in every instance in which it is looked 

 for with a quarter-inch glass,* or even with the half-inch, pro- 

 vided the creature is left at perfect liberty, and is made to 

 move, if not in the right position. It often remains at rest 

 for some time, and then from above looks like a small bright 

 spot at the base of the " tooth ;" or it may occasionally be 

 seen extended over the S-shaped ridge, or even the base of 

 the tentacle. 1 have many times detected it in motion from 

 behind through the intervening substance of the body ; and 

 have noticed it vibrating vigorously long after rupture of the 

 integument and partial discharge of the contents. A Chara 



* I use a quarter-inch glass of IMUischer's, or a l-.5th of Smith and 

 lieck's make. 



