WOBMS. 261 



lucent flesh the points in question. They are not, how- 

 ever, single ; but each protrusile organ consists of a pair 

 of transparent, brittle, glassy rods, shaped like an italic /, 

 of which the recurved points are directed backwards when 

 thrust out from the skin. 



The mode in which these assist the progression of the 

 Worm is well described by Professor Bymer Jones. 

 " The attenuated rings in the neighbourhood of the mouth 

 are first insinuated between the particles of the earth, 

 which, from their conical shape, they penetrate like a 

 sharp wedge ; in this position they are firmly retained by 

 the numerous recurved spines appended to the different 

 segments ; the hinder parts of the body are then drawn 

 forward by a longitudinal contraction of the whole animal 

 a movement which not only prepares the creature for 

 advancing further into the soil, but, by swelling out the 

 anterior segments, forcibly dilates the passage into which 

 the head had been already thrust; the spines upon the 

 hinder rings then take a firm hold upon the sides of the 

 hole thus formed ; and, preventing any retrograde move- 

 ment, the head is again forced through the yielding 

 mould ; so that, by a repetition of the process, the animal 

 is able to advance with the greatest apparent ease through 

 substances which it would at first seem utterly impossible 

 for so helpless a being to penetrate." * 



Implements analogous to these are found in most of the 

 animals of the class Annelida,^ to which the Earth-worm 

 belongs. But in this creature you see them in their sim- 

 plest form : it is to the aquatic Worms that you must look 

 if you wish to see the amazing diversity, complexity, and 

 delicacy of these organs. In these there are one or two 

 pairs of "feet" on each ring, consisting of wart-like pro- 

 minences, which are perforate and protrusile, and through 



* Gen. Outline," 202. 



f From the Latin annellus, a little ring. A large class of animals 

 known under the common name of Worms, 



