214 F. W. GAMBLE, B.SO. 



Flagella are present anteriorly and posteriorly. Mouth anterior, sub- 

 terminal. The pharynx is ellipsoidal, and lies altogether in front of 

 the brain. The intestine is extensive, and corresponds generally to 

 the form of the body. The brain is reniform, the slight concavity 

 being directed anteriorly. A pair of nerves from the anterior and 

 also from the hinder angles are conspicuous ; three other pairs occur 

 (Bohmig, 57, p. 410). Two eyes are present, provided with lenses. 

 The genital aperitive is ventral, and placed a short distance from the 

 hinder end. The testes are scattered in the parenchyma. A muscular 

 vesicula seminalis is placed close to the genital pore. The female 

 organs are of considerable interest, as no one has yet found any trace 

 of the yolk-glands. Since however, it is known that these organs 

 develop late, it is possible that specimens presenting them in a mature 

 condition have not yet been seen. If, on the other hand, yolk-glands 

 are really not present at any stage, their absence would constitute a 

 feature in which this species resembles the genus Acmostoma. The 

 ovaries consist of a lateral row of clear spherical cells extending from 

 the brain to the hinder end, and surrounded by refractive granules. I 

 have not noticed the accumulation of ova behind the brain to which 

 Bohmig refers (loc. cit, p. 316). 



Habitat. — Among littoral weeds, Plymouth (F. W. G.). 



Distribution. — Heligoland (Metschnikoff, 37), Trieste (Bohmig, 57). 



The specimens that I have seen appear to bear a close resemblance 

 to Acmostoma Sarsii, Jensen. The form, colour, eyes, relations of the 

 pharynx, character of the ova, testes, position of the vesicula 

 seminalis, and apparent absence of vitellaria are almost identical in 

 the two species. The presence of a narrow " creeping sole " in 

 Acmostoma is, however, a distinguishing feature. 



32. Plagiostoma sulphureum, v. Graff. PI. XII, fig. 20. 



Length 2 mm. Body very elongate, cylindrical, parallel-sided for 

 the greater portion of its length, somewhat conical in front, tapering 

 posteriorly. Colour to the naked eye orange, the extreme anterior 

 end paler ; two large black eyes are conspicuous. Movements active, 

 the front end being moved about as a flexible and highly sensitive 

 " lip." The tail is provided with strong adhesive cells, by which the 



