203 



THE ANATOMY OF IXVERTEBRATED ANIMALS, 



Superiorly, the notopodium carries two transverse rows ol 

 more slender organs of a similar nature, the setce : the proxi- 

 mal set are much shorter than the distal, but even the latter 

 do not attain a length of more than -^^ of an inch (Fig. 52, 



^)- . . . . : . 



The proximal set are somewhat knife-like in shape if viewed 

 in profile, consisting of a comparativeh' short, straight "han- 

 dle," by which they are imbedded in their sacs, and of a thick, 

 rounded, curved blade, tapering to a fine point at its extrem- 

 ity. Close-set transverse ridges, finely serrated at their edges, 

 and inclined obliquely to the surface of the blade, traverse 

 its convex anterior circumference, leaving the back free. The 

 distal setre (Fig. 52, G) have a very similar structure, but they 

 are much elongated and very slender. The handle is longer; 

 and the blade, little curved and simply set on an angle with 



Fig. 52. — Polynoe squamata. 



A, olytron viewed from above. B. a tooth. C Z), nonropodial cetae. E, F, parts of 



the blade of the pamc, more highly magnified. G, free extremity of a notopodial 



peta. 



the handle, is produced at the end into a long and delicate 

 filament. The base of the blade {E) is beset with incomplete 



