NOTES ON SOME OF THE POLYCH^TA. 343 



classification. . , The distinctions between many of the species are 

 nice, yet exact, and afford a good field for scientific accuracy in 

 microscopic work." 



Bourne* mentions the neuropodial and notopodial setae as 

 variable in the series of Polynoe clava examined by him, but 

 remarks that the characters of equivalent setae were constant. 



After a careful examination of the Polynoidae of the 

 L. M. B. C. collection,! I can scarcely think that the setae are 

 such trustworthy guides in the identification of species as 

 Prof. Mcintosh believes them to be. In the first place, in 

 the individual the setae vary much, as Bourne observes, not 

 only in colour, but in size, in curve, markings, and serrations. 

 I mounted the entire series of parapodia from three examples 

 of Harmotho'e imbricata, and was astonished to find that the 

 amount of variation was very considerable. I was fortunately 

 able to mount entire two or three young specimens of 

 H, imbricata, and there also the difi'erences between the 

 bristles of the young and those of the adult were observable. 

 I did the same for Polynoe clava, with similar result. No 

 doubt, in aberrant Polynoidae like Hermadion assimile 

 (PL VIII), the spines are reliable guides, but no one would 

 require to look at the spines to identify such a form. 



I agree with Bourne, that comparison of equivalent setae 

 is useful, but with all due deference to so high an authority 

 as Dr. Mcintosh, I would feel doubtful of resting the identi- 

 fication of species so much on the character of the setae as 

 he seems to be inclined to do. + I would equally doubt the 

 advisability of trusting too much to the form of the para- 

 podia themselves as is done by Dr. Hj. Theel, in his 



* Trans. Linn. Soc. Lond., ZooL, 2nd ser., vol. ii, p. 349. 



t See Report on the Vermes, p. 144. 



I Compare *' Challenger" Report ou Annelidas, by Professor Mcintosh, 

 F.R.S. Dr. Mcintosh does not state, in many cases, from what segment 

 of the body the bristles are taken. 



