THE ANATOMY OF SOALIBHEGMA INFLATUM. 287 



mentions tlie presence of gills fis one of the diagnostic cha- 

 racters; and Levinsen (I880, p. loo) includes this among the 

 characters of the family Scalibregmidae, but qualifies the 

 statement by adding that gills are present only in older 

 worms, or may also be present in younger individuals. 



Hansen (1882, pp. 34, 35) described a gill-less worm 

 obtained by the Norwegian North Atlantic Expedition as 

 Scalibregma (?) parvum, and Mcintosh (Eumenia 

 jeffreysii, 1868. p. 419; and E. reticulata, 1885, p. 360), 

 Theel (E. longisetosa, 1879, p. 49), and Ehlers (E. glabi-a, 

 1887, p. 169) have referred other gill-less specimens to the 

 genus Eumenia. Levinsen (1883) renamed Theel's speci- 

 men Scaliln'egma longisetosuni ; but this is not satis- 

 factory, as an abranchiate species is thus placed in a genus 

 one of the distinctive characters of which is the pi-eseuce of 

 gills. Cunningham and Ramage (1888, p. 655) recognised 

 that specimens similar to those named by Mcintosh Eu- 

 menia jeffreysii did not belong to the genus Eumenia; 

 they considered them to constitute a new genus — Lipo- 

 branchius. The absence of gills in his specimens (which 

 were 35 — 37 mm. long) was carefully considered by Theel 

 (1879) before naming- them Eumenia longisetosa. Pos- 

 sibly with a view of accounting for the absence of gills in 

 these specimens, or at any rate of minimising the value of 

 these organs as diagnostic, he states that the gills of Eu- 

 menia crassa do not begin to grow until the animal has 

 attained a length of 40 — 50 mm. The absence of gills in E. 

 longisetosa might, therefore, be due to the fact that the 

 specimens were young ones in which gills would have ap- 

 peared later. But this seems scarcely probable, and Theel's 

 statement regarding the formation of the gills of E. crassa 

 at a comparatively late stage of the animal's growth also 

 seems extraordinary, as in many branchiate Polycha^tes the 

 gills are formed in early life when the animal is quite small, 

 e. g. a specimen of Arenicola marina 4 mm. long already 

 bears the full number (thirteen pairs) of gills. Theel's state- 

 ment, moreover, does not agree with that of at least one 



