300 EVENINGS AT THE MICROSCOPE. 



about, of a number of tiny points protruded and re- 

 tracted with rliythniical symmetry through the skin. 

 Its mobility precludes our discerning much more than 

 that these points are very numerous, that they are ar- 

 ran<red in four loiiijitudinal lines, running along the 

 ventral side of the animal — two lines on each side — 

 and that in each line there is a point protruded from 

 each of the many rings of which the Worm's body is 

 made up. 



In order to see a little more of these organs we must 

 sacrifice a Worm ; having killed it, and divided the 

 body in the middle, I cut oif, with sharp scissors, a 

 small transverse portion, say two or three rings, and 

 press the fragment between plates of glass. Now, with 

 a higher magnifying power, we discern in the midst of 

 the translucent flesh the points in question. Tiiey are 

 not, however, single ; but each protrusile organ consists 

 of a pair of transparent, brittle, ghissy rods, shaped like 

 an italic y, of which tlie 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 Kymer Jones. 

 "The attenuated rings in the neighbourhood of the mouth 

 ai"e first insinuated between the particles of the earth, 

 which, from their conical shape, they penetrate like a 

 sharp wedge ; in this position they are firmlj^ retained 

 by the numerous recurved spines appended to the dif- 

 ferent segments; the hinder parts of the body are then 

 drawn forward bv a. longitudinal contraction of the 

 whole animal — a movement which not only prepares 

 the creature for advancing further into the soil, but by 

 BM'elling out the anterior segments forcibly dilates the 

 passage into which the head had been alreadv thrust : 



