1901.] ON THE STEirCTURE AND AKRaNGEMENT OF EARTHWOEMS. 187 



supplied a sense-organ of the supraorbital canal and sent a few 

 twigs to the surrounding skin. 



This somewhat complicated description when compared with the 

 figure will, I trust, make it clear that these two supraorbital sense- 

 organs in Chimcera do not, as was supposed, present an anomaly 

 in their innervation, but receive their nerves in all likelihood from 

 the superficialis as do the other organs of that canal, and in their 

 mode of innervation show a close similarity to those that lie in 

 front of them ; for in both cases the actual nerve-trunk from which 

 the filaments for the individual sense-organs arise is of a compound 

 nature formed by an intimate blending of the superficialis VII 

 with the profundus V, differing only in the fact that in the case of 

 these two sense-organs the union occurs between the smaller 

 branches of the nerves, while in that of the organs in front it 

 involves their main trunks. In both cases the fusion is so com- 

 plete, that it is impossible by simple dissection to say definitely that 

 the fibres derived fi-oin the superficialis terminate in the lateral-line 

 sense-organs, while those of the profundus are distributed to the 

 skin ; but the probabilities that such is the case are so great as to 

 almost amount to certainty. 



3. Contributions to the Knowledge of the Structure and 

 Systematic Arrangement of Earthworms. By Frank E. 

 Beddard, M.A., P.R.S. 



[Eeceived January 31, 190.1.] 

 (Text-figures 50-58.) 



1. On Polytoreutus gregorianus. 



This species was very briefly defined by me five years ago 

 in my Monograph of the Oligochseta \ Since then the publication 

 of descriptions and illustrations of various new species of the 

 genus has decided me to attempt an addition to our knowledge of 

 this remarkable genus by a fuUer account of the form which I 

 named after Prof. Gregory of Melbourne, and which was collected 

 by him in Africa during his espedition of 1894. 



The worm measures 230 mm. in length by a diameter of 9 mm. 

 The number of segments are between four and five hundred^. As 

 might be supposed from their large nuDibers, the segments are 

 veiy short; this is the case with all those lying behind the clitelluin ; 

 those forming the clitellum and those lying in front of it are stout 

 segments as in other earthworms. 



The setce, as in other species o£ Polytoreutus, are in couples, of 

 which the two lateral are more closely approximated to each other 

 than the two ventral. The disproportion of the spaces separating 

 the two lateral setae from each other and the two ventral setae is 



1 Oxford, Clarendon Press, 1895, p. 612. 



^ These ineasuremeuts diifer slightly from those which I originally gave. 



