86 EARTH-WORMS.SUCKERS. 



each side a number of setse which serve them 

 for locomotion. They have neither eyes, tenta- 

 cles, nor jaws. If we cut one of these into two 

 pieces, each piece continues to live, and becomes 

 a perfect animal ; the part of the body which is 

 deficient is reproduced. 



11. The lumbrici (earth-worms) are propa- 

 gated by eggs, which, when laid, are two or 

 three lines in length. In the annexed figure (75), 

 one of them, enclosing a mature embryo, is de- 

 lineated ; the top is closed by a peculiar valve- 

 p. ~ like structure, adapted to facilitate the escape of 



EGG OF THE the worm. The egg commonly has a double yolk, 

 EARTH-WORM. and a couple of young ones are produced generally 

 from each egg. 



" Whoever has attentively watched the operations of an earth-worm, when 

 busied in burying itself in the earth, must have been struck with the seem- 

 ing disproportion between the laborious employment in which it is per- 

 petually engaged, and the means provided for enabling it to overcome dif- 

 "ficulties apparently insurmountable by any animal unless provided with 

 limbs of extraordinary construction, and possessed of enormous muscular 

 power. In the mole and burrowing cricket we at once recognise in the im- 

 mense development of the anterior legs a provision for digging, admirably 

 adapted to their subterranean habits." Every ring of the lumbricus, " when 

 examined attentively, is found to support a series of sharp, retractile spines 

 or prickles ; these, indeed, are so minute in the earth-worm, that on passing 

 the hand along the body from the head backwards, their presence is scarcely 

 to be detected by the touch, but they are easily felt by rubbing the animal 

 in the opposite direction ; a circumstance which arises from their hooked 

 form, and from their points being all turned towards the tail." By the aid 

 of these the animal makes its way in the following manner : " 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 forwards by a longitudinal con- 

 traction 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 on the hinder rings then take a firm hold upon the sides 

 of the hole thus formed, and, preventing any retrograde movement, the head 

 is again forced forward 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 would at first seem utterly impossible for so help- 

 less a being to penetrate." Thomas Rymer Jones Comparative Anatomy, 



12. The family of sucto'ria or suckers comprises the leech, 

 and all anne'lides that are unprovided with setae. The integu- 

 ments are soft ; the body is generally oblong, slightly depressed, 



11. Hotfr are earth-worms propagated? 



12. How is the family of Sucto'ria characterized ? 



