POLYCH^ETA-BENHAM. 4? 



In order to establish the above conclusion, I will give the measurements of the 

 worms. 



A. The small worms, with coloured elytra. 



(1) Nearly complete, with green elytra ; 18 mm. in length, with 28 segments; 

 width at the 7- 12th segment is 4 mm. over the body, measured ventrallly; 

 6 mm. over the neuropod, and 9 mm. over the chaetae. The dorsum is 

 marked with dark-green narrow transverse bars at the sides and with a 

 thin green line on each segment, crossing from side to side. No informa- 

 tion as to the locality. 



(2) Is similarly coloured, though with brown ; the posterior end, after the 



28th segment, is regenerated, with 9-10 minute segments. The length 

 is 22 mm. for these 38 segments. This individual is rather soft ; the 

 dorsal chaetse do not meet their fellows, though they overarch the back. 

 (Station 12.) 



B. Uncoloured individuals, i.e., the elytra are without pigment. 



(3) Length, 23-5 mm. with 39 segments ; width 7 mm. over neuropods. (From 



Station 10.) 



(4) About the same size, though imperfect. Quite similar to number 3. 



No data as to locality. 



The remainder were taken together at Station 1. 



(5) 28 mm. with 41 segments with 7 segments exposed behind the elytra. 



(6) 32 mm. for 42 segments. 



(7) 40 mm. with 44 segments. 



(8) 51 mm. with 45 segments, last 10 segments uncovered. 



(9) Imperfect, but intermediate in size. 



( 10) The largest is 81 mm. with 46 segments, of which the last 13 are uncovered. 



We have here a gradual increase in length with segments added at the hinder 

 end ; and there seems no doubt that, since all agree in their structural details, we are 

 dealing with a single species at different ages. Variation in colour now is so well known, 

 as for instance in H. spinosa, that little reliance can be given or placed on that as a 

 specific character. 



I may add that the largest of the three specimens contained in the French collec- 

 tion measured only 42 mm. with 42 segments, while the two smaller ones were about 

 24 mm. in length. Gravier states that in his specimens the dorsum is unpigmor.*;ed, 

 but in each segment there are two narrow cross-bars of dark violet ; he also notes that 

 pigmentation is less marked in the larger than in the two others. 



It will be well to give in some detail some facts about the specimens from Common- 

 wealth Bay. 



