SECTION IX. — PHYLUM ANNULATA 



An earthworm, a lobworm, and a leech, when compared 

 with one another, will at once be seen to possess certain 

 features in common. Each is bilaterally symmetrical, long 

 and relatively narrow in shape, is transversely ringed or 

 jointed, and has a soft integument ; each has a mouth open- 

 ing towards the anterior end and a smaller anal aperture 

 towards the posterior end. The earthworm and the lob- 

 worm, moreover, resemble one another in possessing a 

 number of bristles, extremely short in the former, disposed 

 regularly in groups along the rings of the body. The ringed 

 or annulate appearance is found, on a closer inspection, to 

 be due to the elongated body being made up of a row of 

 similar parts, the segments or metameres, which are remark- 

 ably uniform throughout the length of the body, not only in 

 external appearance, but in internal structure. A general 

 correspondence is found to exist in the disposition of the 

 internal organs of all the three, and the conclusion is arrived 

 at that they are all members of one phylum. The phylum 

 in question, the Annulata, comprises the earthworms, the 

 class of the marine segmented worms or Annelids to which 

 the lobworm belongs, the leeches and certain other groups. 



1. THE CKETOPODA 



The rows of bristles above referred to as disposed along 

 the segments of the body in the earthworm and the lobworm 



