HERPYfjLOBIUS ARCTICUS. 
407 
with a chitinous fixing organ where it penetrates the tissue of 
the host. The external posterior part is subglobose, white, 
and lackingany vestige of limbs. Posteriorly are twochitinous 
buttresses which support the large egg-sacs, and above are 
six chitin-surrouncled pores, near to which the males are 
attached. The stalk is joined to the middle of the lower sur- 
face of the external j^art, the interior of which is principally 
occupied by the reproductive organs. 
Male. — Minute and sac-like, consisting only of i-eproductive . 
organs, anteriorly drawn out into a conical prolongation which 
is inserted into the female. Forms two large spermatophores 
with long necks. Most of the body of the adult remains 
enclosed in the last larval skin, characterised by the following 
characters: Cephalothorax with two pairs of appendages, 
antenuEe and miixilliped.s, the latter with their last joint 
hooked. Thi'ee free thoracic segments, each bearing a pair of 
birarnous swimming h)gs. Abdomen three-jointed; last joint 
lontjest and bearing- telson with long- bristles. 
O O O 
Specific Characters.^ 
H.arcticus (Stp. and Ltk.). — Female: Anterior portion 
4-5 mm. long-, ^-1 mm. broad. External ^portion li-2 mm. 
long (without egg-sacs). Stalk very thin, diameter one- 
eighth of the length of the external portion. Male (Larval 
skin) : g-4 mm. long. Antennm three-jointed. Maxillipeds 
four-jointed. First and second pairs of thoracic legs with 
external rami two-jointed. 
Habitat. — Greenland, on two species of Polynoid — 
Harmothoe imbricata and Eunoe oerstedi. Gulf of 
St. Lawrence, on Nychia amondseni.- Gulf of Georgia 
Puget Sound, on Harmothoe: Antarctic, on three species of 
Polynoids.® 
‘ Levinsen (9). 
* McIntosh, ‘ Ann. Nat. Hist.,’ 4th series xiii, 1874, p. 262. 
^ Gravier, C., “ Sur quelqne Crustaces parasites anneliclicales prove- 
nant de la seconde expcdetion antarctique fran^aise,” ‘ Coinptes 
Rendiies,’ xliv, 1912, p. 830. 
