354 ME. A. G. BOURNE ON CERTAIN POINTS 



and there, and the products streamed forth. I have kept such animals for a long period 

 after this, and they have been apparently none the worse. I have certainly never seen 

 ova or spermatozoa in the lumen of the nephridium. 



Fig. 26, representing a longitudinal section of a neuropodial cirrus of P. spinifera, is 

 inserted to show the large round connective-tissue corpuscles which exist there in addition 

 to the branched cells. The nerve-filament passing up the axis is also shown. 



Following the example of Sars, Claparede, Grube, and Ehlers, I have rejected Kinberg's 

 and Malmgren's genera, and have usedSavigny's original generic name Polynoe. I have 

 shown that so many of the characters used by these authors to found generic distinctions 

 are variable in the same species, and that with regard to others it is easy to find all 

 intermediate variations between two extreme conditions. 



I quite agree with Mcintosh that the utmost importance may be attached to the 

 exact character of the seta?, but thiuk that he hardly sufficiently insists upon the varia- 

 tion which occurs in these in individuals, and the necessity of comparing equivalent seta?. 

 The seta?, for instance, in the neuropodium of the third body-somite are totally unlike 

 the neuropodial seta? of the somites which follow, and much more resemble notopodial 

 seta?. An immense amount of variation may occur, moreover, in the notopodial seta? in 

 any one parapodium. 



With regard to the elytra, I have spoken of them as structures which do not belong 

 to the parapodium. Their attachment is always to the dorsal surface of the somite 

 proper ; they occur side by side with notopodial cirri in Sigalion and its allies ; and 

 I have observed in P. (Harmothoe) areolata (I have not examined many other species 

 from this point of view) that distinct rudiments of notopodial cirri — the whole of the 

 basal portion, in fact — coexist with an elytron upon the elytron-bearing somite. The 

 elytra have been spoken of as branchial in function ; my sections (P. areolata) show that 

 no blood can pass into them. Although they appear to be attached to the somite over a 

 considerable area, the real attachment is almost linear ; in the central region there is no 

 attachment, and the epidermis is unbroken. Numerous muscles are attached all round 

 this ring, and serve to move the elytron as a whole. Nerves pass into the substance of 

 the elytron (which is quite solid), and, forming a regular network (which I have stained 

 with gold), end in the numerous small papilla?, which are, no doubt, tactile and similar 

 to those Claparede has described upon the cirri. 



Characters of Polynoe clava (Montagu). — These may be summarized as follows : — 

 27 somites ; 12 pairs of elytra, borne upon somites 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23. 

 Median tentacle twice as long as the lateral tentacles, bulbous below the apex, with a 

 terminal filament. Lateral tentacles with similar structure. Palps tapering to a point, 

 beset with six longitudinal series of small papilla?. Normal neuropodial seta? clavate, with 

 talon-like apex, 7 or 8 pairs of pectinated frills, the most anterior provided with 5 long 

 teeth upon its fine edge. Notopodial cirri about twice the length of the parapodium, 

 with the same structure as the prostomial tentacles. Neuropodial cirri half the length of 

 the parapodium, tapering gradually to a point, smooth. Elytron only slightly rough on 

 the surface, margin entire. Anus on the dorsal surface. Pygidiai cirri resemble noto- 

 podial cirri in structure. 



