92 



Mr. E. Eaj 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 

 difiers in no respect from T. rivuloruvi when closely examined 

 bj the naked eye or low powers, the setjB of the dorsal row of 

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

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

 ization the setas of some Polychata. 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 



Tm. 1. 



Fig. 2. 



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

 The setfe 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 setee, both in the dorsal 

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

 resembling those of Lumbriculus, and diiFering very clearly 

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

 setae 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 diff'ers 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 

 Claparbde is grafted and the proper penis. This portion, un- 

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

 Claparfede, is non-glandular, and resembles the corresponding 



