92 



Mr. E. Ray Lankester on the Organization 



The second species of Tuhifex in the Thames I first obtained 

 with Mr. Kent in the Victoria Docks. I have since had speci- 

 mens in abundance from near Barking. In this form, which 

 differs in no respect from T. rivulorum when closely examined 

 by the naked eye or low powers, the setaj of the dorsal row of 

 the first ten segments present, when highly magnified, a form 

 seen in no other Oligocliffitous Annelid, recalling by its special- 

 ization the sctaj of some Pulycha'ta. The bifid apex has its 

 prongs directed forwards, and widely divergent, the interval 

 being occupied by a finely ribbed membrane, which is some- 

 what depressed between the two prongs (fig. 1 h). With these 



Fiir. 1. 



Fig. 2. 



are associated from one to four capillary setse in each bundle. 

 The seta? of the first ten ventral {i. e. on the neural aspect) 

 fascicles are small and of the usual crochet form (fig. 1 a) ; but 

 after the tenth setigerous segment, the seta?, both in the dorsal 

 and ventral fascicles, assume a very marked stout form (fig. Ic), 

 resembling those of LumhriculuSj and differing very clearly 

 from those of T. rivulorum. The webbed or palmate dorsal 

 setge of the first ten segments appear to act in concert as so 

 many oars, propelling the worm by the pressure of their flat 

 surfaces on the water. This species of Tuhifex differs further 

 from T. rivulorum in the narrowness and elongation of that 

 part of the male efferent duct which lies between the enlarge- 

 ment upon which the gland called " seminal vesicle " by 

 Clapar^de is grafted and the proper penis. This portion, un- 

 like what occurs in T. rivulorum or the two species figured by 

 Clapar^de, is non-glandular, and resembles the corresponding 



