Terns) 
VII. On British Annelida. By W. C. M‘Intosa, C.M.Z.8. 
Read May 19th, 1874. 
[Puares LXVIL-LXX.] 
Part 1.—EvrnrosyNIp#, AMPHINOMID.®, APHRODITIDA, PoLyNorp2, AcokTIDA, 
and SIGALIONIDA. 
IN the first of a series of papers on the British Marine Annelida, which I propose to 
offer to the Society, one or two reflections which have occurred during the study of the 
present forms may not be inappropriate, especially as they apply with equal force to the 
succeeding groups. Few students of the Annelida proceed far in their investigations 
before becoming aware that in many of the descriptions of their predecessors there is 
nothing decisive, and that they must wade through many superficial remarks without 
being able to lay hold of any stable character by which to extricate themselves from 
doubt. In some cases it would almost seem that the authors meant their successors to 
spend valuable time to little purpose in vainly endeavouring to find out the exact 
nature of the species, of which they themselves entertained only a hazy conception. 
It would appear in the majority of these instances that such inadequate and unsatis- 
factory descriptions have been due to the fact that the nice distinctions between closely 
allied forms have hitherto attracted little attention and less study. It is impossible, 
for example, to describe too minutely in groups like the Polynoide, in which the 
specific separation rests on so many fine characters. ‘The mere statement that a 
bristle is slender and serrated conveys little more to the mind of an observer than the 
assertion, in comparing the hair of the bat with that of the sheep, that each is 
serrated. Even some of the most distinguished modern investigators of the Annelida 
have failed to appreciate the valuable results derived from a strict and faithful appre- 
hension of the structure of the bristles, the other characters of course being duly 
attended to. If, instead of writing pages of weary Latin descriptions, a few terse 
sentences had been given, and a single characteristic bristle accurately figured by 
the author, very great labour and not a little doubt would have been saved to his 
successors. The characteristic markings at the tips of the bristles of Hermadion pellu- 
cidum and H. assimile, for instance, show how valuable such characters will some day 
be in classification. The same peculiar feature is exhibited by the Gastrolepidia clavi- 
gera of Schmarda in the upper series of the ventral branch of the foot, and in the 
whole of the dorsal bristles; moreover their transparency is remarkable. The di- 
stinctions between many of the species are nice, yet exact, and afford a good field for 
VOL. IX.—PART VII. January, 1876. 35 
