342 



NOTES on some of the POLYCH^TA collected by the 



L. M.B.C. 



By R. J. Harvey Gibson, M.A., F.R.S.E., F.R.MS., 



DEMONSTRATOR OP ZOOLOGY IN UNIVERSITY COLLEGE, LIVERPOOL. 



This paper deals with — 



. (1.) The value of the setae of the Polychseta as specific 

 characters. 

 (2.) The structure of the following Aphroditidae : — 

 (a.) Malmgrenia castanea, Mcintosh. 

 (b.) Hermadion assimile, Mcintosh. 

 (3.) On Pectinaria auricoma, Miiller, 

 and Pectinaria helgica, Pallas. 



1. With reference to the first of the above subjects, a 

 few remarks may appropriately be made here. 



Mcintosh* lays great stress on the importance of the 

 setaB as specific characters, and insists on the accurate 

 delineation of typical examples. In speaking of the setae, 

 he says : — 



" It is impossible, for example, to describe too minutely in groups 

 like the Polynoidse, in which the specific separation rests on so many 

 fine characters The mere statement that a bristle is slender and 

 serrated conveys Httle more to the mind than the assertion, in com- 

 paring the hair of a bat with that of a sheep, that each is serrated. 

 Even some of the most distinguished investigators of the Annelida 

 have failed to appreciate the valuable results derived from a strict and 

 faithful apprehension of the structure of the bristles, the other cha- 

 racters, of course, being duly attended to. The characteristic mark- 

 ings at the tips of the bristles of Hermadion pellucidwn and H. assimile, 

 for instance, shew how valuable such characters will some day be in 



* On British Annelida, Trans. Zool. Soc, Lend., ix, 371. 



