BRITISH MARINE TURBELLARIA. 483 



hatched are without a definitive pharynx, gut, eyes, or brain. 

 They become sexually mature iu three weeks. 



Subfamily CvLiNDRosTOMiNiE. 

 V. Graff's definition of this sub-family (' Monogr.,' p. 409) 

 has been materially altered, owing to Bohmig's researches. It 

 now reads thus (Bohmig, 57, p. 469) : 



Plagiostomidse with a ciliated '^circular groove." 

 The oral and genital apertures combined. A germ- 

 yolk-gland present. Spermotheca present, con- 

 nected with the ovigerous cell-mass ("Keim- 

 lager"). 



Genus 21. — Cylindrostoma, Oersted (21), 



The limits of this genus are not yet satisfactorily defined, 

 v. Graff divided it into prosoporous and opisthoporous forms, 

 according as the mouth was anterior or posterior. The latter 

 have been excluded by Bohmig in his definition of the genus. 

 V. Graff's original extension of the genus is, however, here 

 adopted, pending a thorough examination of the Opisto- 

 pora. 



48. Cylindrostoma quadrioculatum (Leuckart, 23). 



Length '5 — -9 mm. Body colourless, somewhat depressed, 

 rounded in front, tapering posteriorly to a long " tail " beset 

 with adhesive cells. Mucus-rods (" Schleim-stabschen "), 

 of an irregular granular character, occur in the epidermis. 

 Flagella are interspersed among the cilia in front and behind. 

 At the level of the brain a pair of well-marked ciliated furrows 

 are present. Mouth ventral, in front of the brain. Pharynx 

 elongate, cylindrical, extending from the brain to the centre of 

 the body ; its anterior margin is crenulate, and provided with 

 stout flagella. Brain almost cubical. The genital aperture 

 is combined with the mouth. This remarkable discovery, made 

 by Bohmig, corrects former mistakes due to misleading com- 

 pression preparations. The testes form large follicular masses 

 surrounding the brain. The different stages in the develop- 



