

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, is long 

 and relatively narrow in shape, is transversely ringed or 

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

 opening towards the anterior end and a smaller anal 

 aperture towards the posterior end. The Earthworm and 

 the Lobworm, 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 three animals mentioned, and the con- 

 clusion is arrived at that they are all members of one phylum. 

 The phylum in question, the Annulata, comprises the 

 class of the Earthworms and the Marine Segmented Worms 

 or Marine Annelids to which the Lobworm belongs, the 

 Leeches, and certain other groups. 



