ANNELIDES. 



n 



The Head (fig. 8) has various appendages. There are usually 

 one or two pairs of eyes placed on the dorsal aspect behind the 



No. IV. 



antennae. In the subcephalous and acephalous tribes eyes are gene- 

 rally absent. They are always sessile, simple, and immoveable. 



AntenncB (figs. 8 « & \l a) exist only in cephalous genera. They 

 are soft, setaceous filaments, varying in number from one to five, and 

 distinguished from the other appendages by arising directly from the 

 head. They are usually jointed at the base, and are not retractile. 



Palpi (fig. 8^) are seldom found. They are also soft filaments, en- 

 tire or jointed, and originate externally from the sides of the oral orifice. 



Tent acuta (figs. St & 9t) are the soft setaceous or filiform non- 

 retractile processes which arise from each side of the cephalic segments 

 in pairs, and spread laterally. They are sometimes jointed ; often 

 very long, and remarkably contractile in the acephalous genera. 



The Mouth (fig. 1 1 m) is underneath the head, and is a round or 

 transverse entrance to the oesophagus and intestinal canal. It has 

 usually a plain margin. In the acephalous genera it is terminal and 

 emaxillary, but occasionally furnished with external tentacles. In 

 the subcephalous it is subterminal or ventral ; and in the cephalous 

 nearly terminal, looking forwards horizontally. 



The Mouth in the cephalous tribe is almost always furnished with 



