314 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



three in the dorsal ones, where they are accompanied by 

 capilliform and sometimes by pectinate setae. More 

 posteriorly they decrease in size and number, soon 

 dwindling down to two in a bundle, and near the posterior 

 end of the body it is usual to find only one small seta in 

 each bundle. 



The pectinate setae are, as already mentioned, less 

 numerous than the uncinate type, and are confined to the 

 dorsal bundles of the anterior segments. There, there- 

 fore, it is possible to find in the same bundle setae of 

 three different kinds : capilliform, uncinate, and pecti- 

 nate, the total number rarely exceeding six: The 

 pectinate setae resemble the uncinate of the dorsal bundles 

 in general form. The only difference between them is the 

 presence, in the pectinate form, of subsidiary prongs 

 between the two main divisions of the seta (PI. II, 

 fig. 6, c). These subsidiary prongs are figured and 

 described by Mcintosh, Lankester and Beddard. Their 

 number varies from 1 to 4, the latter number occurring 

 most rarely. 



I have not yet been able to identify the webbed setae 

 described by Lankester (1871). He discusses at some 

 length the form of the sigmoid setae in this worm. He 

 states that he has often seen sigmoid setae, in the dorsal 

 bundles of the first ten segments, which are provided with 

 a web between the two prongs. Benham, who also 

 investigated this species, could not identify the web. 

 During my observations on the setae I have particularly 

 looked for the appearance of this web, but have always 

 failed to find it. A possible explanation of this difference 

 of opinion is that Lankester was looking at the pectinate, 

 setae which do occur in the dorsal bundles of these 

 anterior segments only, and mistook the subsidiary prongs 

 for a continuous web stretching across between the two 

 main prongs. Again, Lankester recounts how he has seen 



