394 R. VON LENDENFELD. 



From the upper margin of this protoplasinatic sac which 

 surrounds the vesiclCj a conical^ stout and pointed filament, the 

 cnidocil, projects. This is about as long as the vesicle is 

 broad, and is situated in such manner oblique to the surface as 

 to form with it an angle of 45°. This angle is very constant. 

 The cnidocil always points in a centrifugal direction, that is to 

 say the cnidocils on the tentacles point towards the ends of the 

 tentacles, those on the body point towards the mouth, and so 

 on. The cnidocils invariably point in that direction from which 

 a foreign body is most likely to approach the animal. 



The vesicle itself possesses a very distinct, tough, and appa- 

 rently elastic membrane. It is closed on all sides except the 

 anterior end, where a circular aperture, about a quarter as wide 

 as the vesicle, is situated. This aperture leads into a very long 

 tube, when the cnidoblast has exploded. This tube is about 

 twenty times as long as the cnidoblast and tapers towards the 

 endj which appears pointed. It is surrounded by one or two 

 spiral lines of minute hooks or bristles which are often very 

 large and conspicuous at the base, but which rapidly decrease 

 in size distally and become invisible even with the highest 

 power near the end. The tube is probably closed at the end. 



This tube can be ejected with great force from the capsule of 

 the cnidoblast, where it is coiled up very regularly before the 

 explosion. The explosion inverts this tube hanging down 

 from the orifice of the capsule into its interior, so that the 

 external surface of the coiled-up tube becomes the internal 

 surface of the ejected tube and vice versa. The well-known 

 poisonous eflFect of these cnidoblasts is due to a poison which is 

 contained in the interior of the coiled-up tube, and which, as 

 the tube is inverted, comes to be situated on the outer surface. 

 The tube penetrates, by the force of its ejection and in conse- 

 quence of its small size, soft foreign bodies which may come in 

 contact with the animal, and so the poison is transmitted into 

 the body of the victim. Whilst Mobius and others have 

 studied the tube and capsule, the discovery of the cnidocil was 

 made by F. E. Schulze. 



After these facts had been made known, the question arose 



