472 F. W. GAMBLE. 



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 Acraostoma 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. XLI, 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 'Hip." The 

 tail is provided with strong adhesive cells, by which the animal 

 is securely fixed at will. The epidermis contains numerous 

 rhabdites of a bright yellow colour, to which the tint of the 

 animal is due. Mouth below, pharynx behind the brain. 

 The pharynx is very small, the musculature being slightly 

 developed. Numerous glands surround it. The intestine 

 occupies the central part of the body, and is enclosed ante- 

 riorly by spherical glands. The genital aperture lies a 

 short distance from the hinder end on the ventral surface. 

 The small testes are placed behind the centre of the body in the 

 middle line. The spermatozoa have a very characteristic 

 form. They are divisible into a broad head, and a narrow 

 pointed tail. A dark transverse band separates the head end 

 off as a pointed lid. Down the centre runs a spiral thread. 

 The ova develop from a median cellular mass which, according 



