NOTES ON THE NAIDIFORM OLIGOCH^TA. 351 



longei' and thinner than those which follow, and the ventral 

 setse of the majority of the segments are a little thicker and 

 shorter than the dorsal setae (PI. XXVII, fig. 5). 



Modified genital setae are present in sexual individuals. They 

 are the ventral setse of segment v. There is no evidence that 

 they represent any interpolated segment. The ordinary seise 

 doubtless drop out from the ventral bundles in that segment 

 during the breeding season, and are replaced by the modified 

 genital setae. There are usually three in the bundle. They are 

 very stout, and longer than the ordinary setae, and they possess 

 a mere rudiment of the crotchet at the free extremity. 



In the budding individual the arrangement of the setae in a 

 well-advanced bud is shown in PL XXVI, fig. 2. In the new tail 

 the series of seta bundles are seen to fade away gradually as one 

 passes backwards — that is to say, the most posterior bundle is 

 the youngest. In the new head there are three pairs of ventral 

 seta bundles, only the new head assumes from the first its 

 adult character (compare this with Pristina). 



The pharynx occupies about three segments, and at its sides 

 and posterior to it occur two large glandular masses (Pis. 

 XXVI, XXVII, figs. 2 and 3, ph. gl.), which are ' possibly 

 groups of unicellular salivary glands. The " stomach " is well 

 marked, and lies in segment viii; the intestine is narrow in the 

 following segment, and then widens out. 



The dorsal and ventral vessels are clearly defined through- 

 out the whole length of the worm. They communicate with 

 one another by three pairs of branching lateral vessels in seg- 

 ments II to IV, and by three pairs of larger unbranched 

 '' hearts " in segments v to vii. 



It is exceedingly interesting to note that in the newly 

 budded regions and other regions of active growth, as in all 

 tail regions, the dorsal and ventral vessels are joined by com- 

 missural vessels in every segment, and that this is therefore 

 doubtless the primitive arrangement ; and the suppression of 

 the commissural vessels in all except certain anterior segments 

 indicates a particular kind of cephalization (PI. XXVI, fig. 2). 



I was unable, even after repeated examination, to discover 



