HERPYLLOBIUS ARCTICUS. 
403 
vacuolated tissue in the external body, as well as with the 
“gut” spaces, and it is probably by this means that 
nourishment is carried to the reproductive organs, which 
occupy practically the whole of the external body. 
As to the life-history, there is nothing known. There is 
probably a free-swimming stage in the female, as in the allied 
Leinseopodidae, as otherwise one cannot account for the 
infection of new Avorms. It is probable that the males become 
attached to the female at an early stage, as is the case in 
Rhizorhina; having no gut and no apparent means of 
absorbing nutriment they must be short-lived. 
No stages of development were to be found in the eggs. 
V. Comparison with Allied Genera. 
Hansen, in his work on the Choniostomatidae (4), gives an 
account of the relationships of Uerpyllobius and the allied 
genera. Previously^ he had established the family Herpyllo- 
biidie containing the seven genera: Herpyllobius (Stp. 
and Ltk.), Eurysilenium (M. Sars), Rhizorhina 
(H. J. H.), Trophoniphila (McIntosh), CEstrella (McIn- 
tosh), Saccopsis (Lev.), and Bradophila (Lev.). 
Trophoniphila bradii is described by McIntosh^ as 
adhering to the bases of the branchiae of the worm Tro- 
phonia, while CEstrella levinseni® is described by the 
same author from Ehlersiella; in both cases, however, an 
extremely short description is given, so that it is only possible 
to refer thetti to this family without any comparison with the 
other groups. The female of Rhizorhina forms a short 
slender stalk Avhich ]>ierces the skin of the gill of its host 
(A m pel i sc a) ; in this stalk are two tubes which, on entering 
the skin of the host, separate and ramify irregularly through 
the gill, sometimes entering into the body of the host. In 
Herpyllobius and Eurysilenium the stalk pierces the 
' Hansen, “ Rliizorhina anipelisca,” loc. cit. 
- McIntosh, “ Report on the Annelida Polychseta,” ‘ Report Sclent. 
Results of H.M.S. “ Challenger,” ’ xii, 1885, p. 368, pi. xxxviA, fig. 4. 
^ McIntosh, loc. cit., p. 477, pi. xxxixA, fig. 11. 
