252 F. W. GAMBLE, B.SC. 



cells" in the parenchyma). C. flavibacillum (dorsal surface 

 very convex, no "yellow cells," sides of the body only 

 slightly flexed ventrally). 



Section B. — Rhabdoccela. 



3. With sexual and asexual reproduction. Female accessory organs 

 absent - Family Microstomidae. 



a. Sexes separate. Head with a pair of lateral grooves. A pre- 



oesophageal caecum present - - Genus Microstoma. 

 Species : — M, grcenlandicum (eyes absent, a red spot usually 

 present anteriorly). 



b. Hermaphrodite. Proboscis present. A posterior and some- 



times lateral bundles of setae only) - Genus Alaurina. 

 Species: — A. Glaparedii (proboscis with numerous papilla?, 

 and a pair of ciliary tufts at its base ; posterior bundle of 

 setae only). 



4. With one or two genital apertures. Male accessory organs 

 present. Pharynx usually mid-ventral, rosulate (i.e. rosette-like) 



Family Mesostomidae. 

 I. A single genital aperture, two germaria, and two vitellaria. 

 Accessory reproductive organs absent 



Sub-family Promesostominae. 

 a. Characters of sub-family - - Genus Prombsostoma. 

 Species : — P. marmoratum (copulatory organ coiled, crosier- 

 like). P. ovoideum (penis pyriform, pigment-cup of eye 

 simple). P. solea (pigment-cup of eye with hook-like 

 process over outer surface of lens). P. lenticulatum (copu- 

 latory organ provided distally with radial triangular ridges). 

 P. agile (copulatory organ curved, simple). 

 II. Two genital apertures. The male pore in front of the female. 

 Germarium single ... Sub-family Byrsophlebinae. 

 a. Characters of sub-family - - Genus Byrsophlebs. 

 Species : — B. Graffi, (vitellaria unbranched : copulatory organ 

 widely funnel-shaped, the terminal margin with a triangular 

 projection). B. intermedia (vitellaria branched, copulatory 

 organ elongate, the terminal margin entire, and with a 

 curved chitinous spur). 



