484 F. W. GAMBLE. 



ment of the spermatozoa can be well observed. Behind the 

 penis are a pair of short, wide vasa deferentia, which 

 open into a highly glandular vesicula seminalis. The penis 

 is a muscular, cup-shaped organ receiving both sperma- 

 tozoa and granule-secretions from the vesicula, which it 

 transmits through the genital atrium (underneath the pharynx), 

 and so to the exterior. The spermatozoa are elongate, wider 

 in front than behind. The central axis of the tail is markedly 

 granular, and is continued forwards as a spiral thread, wound 

 three times round the surface of the '' head.'' The posterior 

 end of the body is occupied by the large spermotheca. The 

 germ-yolk-gland is composed of an anterior vitelline, and a 

 posterior germinal portion. 



Habitat. — Kilmore, Skye (Claparede) ; abundant in tide- 

 pools, Millport (v. Graff) ; among Ptilota, Ceramium, and 

 other algae, Plymouth (F. W. G.). 



Distribution. — Faroe, west coast of Norway (Claparede 

 and Jensen), Heligoland (Leuckart), Ostende (van Beneden), 

 Sebastopol (Uljaniu). 



49. Cylindrostoma inerme (Hallez, 50). PL XXXIX, fig. 4. 



Length 1 mm. Body oval, broadly rounded in front, 

 tapering behind, of a bright yellow colour. Opposite the level 

 of the brain, right and left, are a pair of lateral grooves, bordered 

 by long cilia. The epidermis contains masses of granular 

 yellow pigment and rhomboidal rhabdites. Mouth ventral, 

 behind the brain. The pharynx is cylindrical, with a crenulate 

 anterior margin. The genital organs resemble those of Cyl. 

 quadrioculatujn very closely; a spermotheca, however, 

 is absent. 



Habitat. — Among fine red seaweeds, Plymouth (F. W. G.). 



Distribution. — Wimmereux (Hallez) . 



This species exhibits very great similarity to Cyl. Kloster- 

 manni, Jensen, especially in form, colour, and general anatomy. 



