POLYCHEHTA FROM THE N.E. PACIFIC. 987 
(2) The Sete.—A good deal of time has been spent in 
endeavouring to fix the value of the notopodial sete of the 
anterior region as a basis of classification. It must, however, be 
stated that the results of this enquiry are entirely negative. The 
variation in the shape of the sete is almost endless, and seems to 
occur indiscriminately in species and individual. The dorsalmost 
sete in each parapodium are nearly always lanceolate and 
symmetrical. Individual variations occur even here in the 
Text-figure 10. 
Phyllochetopterus anglica. 
Series of notopodial sete from anterior region. 
length and thickness of the head, and substantial modification in 
the more ventral sete. The followi ing rough classification of types 
of modification may be given as indicating the range of 
variation :— 
J. Shortening of the head, which remains symmetrical (text- 
Tey Oh Age): 
IT. An increasing asymmetry of the head. 
(a) The head remains long and is drawn out into a 
long asymmetrical tip (text- fig. LOR CSD): 
(b) The head is much shortened, with a short tip and a 
broad edge (text-fig. 10, E). 
