ASHWORTH, AN ACCOUNT OF ARENICOLA LOVENI KINBERG. 7 



There is no trace of neuropodia or neuropodial setae or 

 of gills on either side of this twentieth segment. 



The type specimen is, therefore, abnormal in that it pos- 

 sesses an additional chaetigerous segment but this extra seg- 

 ment is not provided with fully developed parapodia; its 

 notopodia are smaller t han those of the preceding segments 

 and it possesses no neuropodia. Kinberg's figure is correct 

 in its representation of this extra segment. This figure is, 

 so far as I am aware, the only one of any caudate Arenicola 

 showing a chaetigerous segment additional to the normal 

 number. There is such a remarkable constancy in the 

 number of chaetigerous segments in the caudate species of 

 Arenicola that the presence of an extra pair of notopodial 

 setal tufts in Kinberg's figure called forth Professor Fauvel's 

 remark that this might be due to an error of observation. 

 Cases in which extra notopodia, neuropodia and gills are pre- 

 sent in caudate Arenicolidae are rare. Among some thousands 

 of specimens of A. marina which have passed through my 

 hands during the last few years, I have seen only three which 

 show an extra pair of notopodia, five with an extra pair of 

 neuropodia, three with an extra pair of complete parapodia 

 (notopodia and neuropodia) and seven with a complete chaeti- 

 gerous and branchiferous twentieth segment. Out of över 

 one hundred specimens of A. claparedii examined. I have 

 seen only one which exhibits an abnormality of thisnature; 

 this specimen has an extra (twentieth) notopodium and neuro- 

 podium, but on one side only. 



Neuropodia are clearl}^ visible on all the chaetigerous 

 segments of A. loveni. On specimen No. 4 the groove of the 

 first neuropodium is about 1 mm. in length, that of the sec- 

 ond 2 mm., of the third 4 mm., of the fourth 7 mm., and 

 of the fjfth, sixth and seven th 12 mm. The groove thus 

 exhibits a rapid elongation in successive segments until in 

 the fifth, sixth and seventh segments it attains its maxi- 

 mum length of about 12 mm., and almost reaches the mid- 

 ventral line. The right and left neuropodial grooves in this 

 region of the body are separated ventrally by a distance 

 of only a little över 1 mm. In the following segments the 

 neuropodial grooves are sligbtly shorter, they gradually di- 

 minish from 11,5 mm. in length in the eighth segment to 

 9,5 mm. in the nineteenth segment. The neuropodia of the 



