36 DARWINISM STATED BY DARWIN niMSELF. 



diameter had a neck || (10*583 millimetres) in length, 

 and yfg- of an inch (-254 millimetre) in breadth. On 

 each side of the orifice there is a long spiral arm, or tube ; 

 the structure of which will be best understood be the fol- 

 lowing illustration : Take a narrow ribbon and wind it 

 spirally round a thin cylinder, so that the edges come 

 tnto contact along its whole length ; then pinch up the two 

 edges so as to form a little crest, which will, of course, 

 wind spirally round the cylinder, like a thread round a 

 screw. If the cylinder is now removed, we shall have a 

 tube like one of the spiral arms. The two projecting edges 

 are not actually united, and a needle can be pushed in easily 

 between them. They are indeed in many places a little 

 separated, forming narrow entrances into the tube ; but 

 this may be the result of the drying of the specimens. 

 The lamina of which the tube is formed seems to be a 

 lateral prolongation of the lip of the orifice ; and the 

 spiral line between the two projecting edges is continuous 

 with the corner of the orifice. If a fine bristle is pushed 

 down one of the arms, it passes into the top of the hollow 

 neck. Whether the arms are open or closed at their ex- 

 tremities could not be determined, as all the specimens 

 were broken ; nor does it appear that Dr. Warming ascer- 

 tained this point. 



So much for the external structure. Internally the 

 lower part of the utricle is covered with spherical papillse, 

 formed of four cells (sometimes eight, according to Dr. 

 Warming), which evidently answer to the quadrifid pro- 

 cesses within the bladders of Utricularia. These papilla 

 extend a little way up the dorsal and ventral surfaces 

 of the utricle ; and a few, according to Warming may 

 be found in the upper part. This upper region is cov- 

 ered by many transverse rows, one above the other, of 

 short, closely approximate hairs, pointing downward. 





