224 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



possesses an entire margin, but later this tends to break 

 up from the edge inwards, thus giving rise to the minute 

 teeth or processes which are usually seen on full-grown 

 setse. The notopodial setse may attain a length of 7*5 mm. 

 (in a specimen 250 mm. long). 



Each neuropodial chseta or crotchet consists of a 

 shaft, generally somewhat curved, bearing at its distal end 

 a beak-like rostrum placed at an angle to the shaft vary- 

 ing from about 90° to about 130° (figs. 15-18). There is 

 generally a slight dilatation of the shaft near the middle 

 of its length. Near the end of most chsetee from young 

 specimens, immediately behind the rostrum there are 

 visible two or more minute pointed teeth, the tips of which 

 are directed towards the tip of the rostrum, while below 

 the rostrum at its junction with the shaft there is often a 

 minute process — the subrostral process. On careful 

 focussing slightly above the level of the teeth and 

 subrostral process there comes into view a number of 

 other fine teeth situated on the sides of the rostrum, so 

 that the latter projects from the centre of a series of teeth 

 arranged round its base. The small subrostral process 

 marks the position of the base of the lowest (and often 

 the smallest) tooth of the series. Only unworn chsetae 

 show these lateral teeth. By isolating the entire band 

 of neuropodial chseta? the number in each neuropodium 

 and the different stages in their growth may be seen. 

 New chsetee are formed at the ventral end of the series, 

 the rostrum being first formed, then the teeth, and finally 

 the shaft which is at first comparatively short (fig. 18). 



The neuropodia of the anterior segments are short 

 and contain few setse, but those further back extend by the 

 addition of crotchets ventrally so as to almost reach the 

 mid-ventral line. The neuropodia of young specimens 

 contain very few crotchets, but in old specimens there is 



