82 ALFRED GIBBS BOURNE. 



Nervous System. 



I have nothing to add to Beddard's account of this struc- 

 ture. We have at present very few criteria for any useful 

 comparison of the nervous system in different worms. It is, 

 however, well known that there is less variation in the nervous 

 system as it occurs in various worms than in almost any other 

 system of organs. This fact — the constancy in structure of 

 the nervous system in groups where most other organs vary 

 greatly — so marked among earthworms and leeches, for in- 

 stance, and so different from what occurs in planarians and 

 nemertines, will doubtless acquire great interest when we 

 know more as to the causes of variation in these lower groups 

 of animals. 



Generative System. 



It would be going altogether beyond the scope of this paper 

 to discuss in any detail the relation of this system as it occurs 

 in Megascolex to that of other earthworms. I give a brief 

 account only of the arrangements obtaining in Megascolex. 



As the only points in which the structures in question differ 

 greatly from those described by Beddard in " Pleurochseta " 

 are such as anyone acquainted with the additions which have 

 been made to our knowledge of this system of organs since the 

 publication of Beddard's paper would have predicted, I shall 

 not compare my account with Beddard's in detail. 



Testes. — The testes (fig. 3) occur in segments x and xi, 

 and are attached to the septa bounding these segments ante- 

 riorly, as is usually the case. 



Seminal Funnels. — The seminal funnels lie of course in 

 the same segments, and are attached to the septa bounding 

 these segments posteriorly. 



Vasa Deferentia. — The vasa deferentia, which are of 

 course connected with the funnels, are exceedingly minute. 

 The two on each side soon join together, and, running back- 

 wards, embedded in the longitudinal muscular layer, open into 

 the muscular duct of the prostatic gland on each side, close to 



