SPECIES OF THE GENUS AULODRILUS. 



965 



high and low. In the taller portions near the inner margin are 

 the nuclei. The muscular sac is smaller in this species; it is 

 about 140 ju in length and 114/x in height. 



The sperm and ovisacs are formed here by extension backwards 

 of septa 9/10 and 10/11 respectively. 



The peripheral portion of the body-cavity in the 9th segment 

 is separated here also by a partition as in A . kashi. 



The ovaries are large and attached to the posterior face of 

 septum 9/10 near the ventral parietes lying in the 10th segment. 



The spermathecse lie in the 9th segment ; in structure they are 

 similar to those in the other species, except that the duct here is 

 somewhat smaller. 



Text-figure 9. 



coe/n. s. 



i^as. d. 



gl-pe.s.s. 



Longitudinal section through vas deferens apparatus of 

 Aulodrilus stephensoni. X 220. 



The present species is principally distinguished from the former 

 by the position of the genital organs, which here lie in segments 

 9 and 10. The seminal funnel lies in the 9th segment, while the 

 restof the efferent apparatus occupies the 10th segment. The sperm- 

 sac and ovisac are formed by septa 9/10 and 10/11. The spermi- 

 ducal chamber is very shallow and lies in segment 10. The 

 uncinate setae are somewhat different from those of the other 

 species, and the penial setae are the modified setse of the 10th 

 segment. 



(5) Kemarks on the Systematic Position of these Worms. 



It will be apparent from the above description that Aulodrilus 

 must be referred to the family Tubificidse, although in A. kashi 

 the anterior position of the genital organs, which lie here in 

 segments 6 and 7, suggests a position closer to the Naidid^e, in 

 which family these organs lie in segments 5 and 6. In A. stephen- 

 soni however, the sexual organs are present in segments 9 and 

 10, though in other structural details there does not seem to be 

 any marked difference between the two species. This clearly 

 decides the position of this genus in the Tubificidse. Another 

 point, in which these worms resemble theNaididae, is the presence 



Proc. Zool. Soc— 1922, No. LXV. 65 



