460 PROP. HARU RAM MEHRA ON THE 



dorsal. Strong ciliary movements were seen in the posterior part 

 of the gut, the direction being forwards; antiperistaltic con- 

 tractions were also noticed to be taking jjl-'i-ce over some length 

 of this part of the tube. 



The blood is yellowish, and without corpuscles. The dorsal 

 vessel lies on the left side of the alimentary canal near the 

 ventral surface as far as septum 5/6, where it becomes dorsal, 

 and lies over the pharynx ; it is sun^ounded by chloragogen cells, 

 or in the region of the pharynx by the pigment previously 

 mentioned. It bifurcates near the anterior end of the animal, 

 and the branches, turning ventrally, unite to form the ventral 

 vessel at the level of the first ventral setal bundles. There are 

 four pairs of lateral commissures in the pharyngeal region, which 

 form a plexus ; behind this, from segment vi. onwards, there is 

 a commissure on the anterior face of each septum, — in some 

 specimens, however, these were only seen as far back as segment 

 xvi. The body-wall is devoid of capillaries. 



The first nephridium lies in segment vii. 



The cerebral ganglion is large and bilobed, deeply indented in 

 front and behind. The ventral nei-ve-cord has an irregular 

 lobulated outline, ganglia not being clearly distinguishable. 



Text-figure 2, 



XI ovis 



^,^^g^n5^^^tesii|!^^S 



^^Pt 



M^ 



Genital region of Nais pectiuata var. inasquaUs. Atr., atrium ; cj.d., ejaculatory 

 duct ; /em./., female funnel; ov., ovum; oyis., ovisac ; sep. 4/5,5/6, and 

 6/7, tlie septa between segments iv. and v., v. and vi., and vi. and vii.; 

 s.f., seminal funnel ; sp.s., sperm-sac ; spth., spermatlieca ; v.def., vas 

 deferens ; ^., .yolk ; S > male aperture. X ca. 120. 

 Text-figs. 2 and 3 are semidiagrammatic, and are compiled from several 

 successive vertical sections. 



Genital Organs (text-fig. 2).— As usual in the Naididse, the 

 gonads appear first, and disappear entirely before the rest of the 

 genital apparatus has reached its full development. 



The testes are a pair of ovoid bodies attached to the posterior 

 face of septum 4/5. The ovaries are similar in appearance in the 

 living specimen, but smaller ; they arise from the posterior face 

 of septum 5/6. 



The seminal vesicle is formed soon after the appearance of .the 

 gonads, as a backward bulging of septum 5/6, which later on, 



