HEAD 



261 



more than the greatly subdivided and enormously elongated palps, 

 as both Pruvot l and Meyer 2 have shown. In such forms as 

 Jfaplobranchus and Ampliicorine the process of subdivision 

 (branching) has only gone a short way. In all the Sabelli- 

 formia each filament, in addition to its sensory function, aids in 

 conveying food to the mouth by the action of the cilia, and has a 

 blood-vessel within, thus acting as a respiratory organ. The 

 filament may carry compound eyes (Fig. 143) either at its apex 

 (Branchiomma) <jr at intervals along its course (Dasychone). 



In the family Serpulidae one (rarely two) of the most dor- 

 sally placed gill filaments is enlarged terminally, and acts as a 



FIG. 133. A,Anterior end 

 of Polydora enlarged. 

 a, Prostomium ; x, 

 frontal ridge ; I, peri- 

 stomium ; c', its long 

 cirrus; 11,111, etc., the 

 following segments ; c, 

 gill : B, head of Sabel- 

 lid ; P, palps (branchial 

 crown) ; t, position of 

 tentacles ; I, processes 

 of upper lip membrane ; 

 I, peristomium raised 

 into a collar ; II, III, 

 IV, following seg- 

 ments. 



stopper or " operculum," which closes the mouth of the tube 

 when the animal withdraws into it. Further, in Spirorbis this 

 operculum is grooved on one side, and serves as a brood pouch in 

 which the eggs undergo development (Fig. 184, p. 341). It will 

 be seen, therefore, that the palps may be very important organs 

 for the life of the worm, and they are no less interesting to the 

 comparative anatomist, serving as they do as an excellent illus- 

 tration of the various uses which Nature finds for one and the 

 same organ. 



In the other sub-Orders the prostomium carries neither palps 

 nor tentacles. 



1 Pruvot traced the nerve supply to these organs, and thus established their 

 homology. Arch. d. Zool. Exptr. (ser. 2) iii. 1885, p. 211. 



- Meyer, "Stud. ub. d. Korperbau der Anneliden," ML Zool. Slat. Ncapcl, vii. 

 1887, 'p. 592 ; viii. 1888, p. 462. In this work a great number of important and in- 

 teresting anatomical facts are recorded with respect to the Terebelliformia and 

 Sabelliformia, as well as certain details as to the structure and development of the 

 nephridia. 



