462 F. W. GAMBLE. 



a chitinous investment for both the duct of the seminal and 

 granule-vesicles. 



i. Typici. 



22. Macrorhynchus Naegelii (Kolliker, 17). PL XXXIX, 

 fig. 5; PL XL, fig. 15. 



Length 2*2 mm. in my largest specimens ; v. Graff states 

 that he has not seen larger ones at Millport, while Mediter- 

 ranean examples range up to 4 mm. Body similar to Acro- 

 rhynchus in shape, cylindrical, bluntly pointed in front, 

 broader behind. Colour variable. Proboscis usually white, 

 the rest of the body dusky brown, through which the testes, 

 ovaries, and penis can be indistinctly perceived with a hand- 

 lens. Claparede (36) has described a variety from St. Vaaste- 

 la-Hogue, which was white with a median dorsal yellow streak. 

 A similar variety occurred at Plymouth (fig. 5). The colour 

 was brown; at the base of the white proboscis and in the 

 middle line was a yellow spot, visible in all positions of the 

 auiraal ; proceeding from this backwards along the mid-dorsal 

 line was a bright yellow streak. These colours appear to be 

 due to pigment in the parenchyma. Small rhabdites are 

 plentifully developed in the epidermis, and the epithelium 

 of the proboscis contains oval, highly refractive bodies, 

 "Neniatocysteu entsprechendeu Gebilde'' (v. Graff, ' Monogr./ 

 p. 323). The histology and relations of the proboscis have 

 been fully elucidated by v. Graff. The brain, bearing two 

 eyes provided with lenses, is placed behind the proboscis, and 

 behind this again is the spherical pharynx. The common 

 genital pore lies behind the centre of the body. It leads 

 into a very extensive atrium, the chitinous lining of which 

 extends into the common passage receiving an anterior male 

 subdivision and a posterior female portion. The testes 

 occur at the sides of the body. The vasa deferentia unite 

 with the contents of an accessory gland. The secretion of the 

 granule-gland, however, is enclosed in a special sac, the 

 lower part of which is chitinous. Its free edge is usually 

 provided with a curved " spur," of variable form. This may 



