BRITISH MARINE TURBBLLARIA. 461 



of the pharynx. The vasa deferentia unite in a sperm- 

 vesicle, close to which is the granule-vesicle. The long 

 muscular cylindrical penis receives both secretions, and is en- 

 closed in an inner chitinous sheath and an outer muscular one. 

 The armature is in the form of hooks with rounded basal ends. 

 The hooks vary in size and shape, and are disposed as in v. 

 Graff's pi. X, fig. 17, of his 'Monographic.' The genital 

 aperture is surrounded by numerous glands. The ger- 

 maria lie at the sides of the penis. The reticular yolk- 

 glands are of considerable extent. 



Habitat. — In tide-pools, and among Pucus and Laminaria 

 below the surface of the sea. Kilmore, Skye (Claparede) ; 

 Millport (v. Grafi") ; Plymouth ; Port Erin, Isle of Man 

 (F. W. G.). 



Distribution. — Bergen (Jensen), Heligoland (MetschnikoflP). 



The well-developed musculature of these forms enables them 

 to resist compression without rupture. If a mature individual 

 be treated in this way the various parts of the genital apparatus 

 stand out with diagrammatic clearness. 



This species, closely similar to the next in external appear- 

 ance, can be distinguished by the presence of the common 

 muscular envelope round the vesiculse seminales and granu- 

 lorum. 



Genus 13. — Macrorhynchus, v. Graff. 



Acrorhynchinse with a common genital aperture, 



two germaria, and paired elongate testes. Vesi- 



culse seminales and granulorum distinct, the 



duct of the latter with a special chitinous tube 



('Monogr.,' p. 321). 



Von Graff divides this genus into two subdivisions : — 



i. Typici. — Those in which a poison-dart (Gift-Stachel) is 



absent ; duct of the vesicula seminalis without chitinous 



armature, ii. Veneno si. — Those provided with a poison-dart ; 



