JOHNSON: POLYCHAETA OF PUGET SOUND REGION. 395 
Nephridialpapillae extraordinarily long in large specimen, fully 
equal to ventral cirri; begin on the sixth somite and extend to the 
eighty-tirst in the larger, and to the seventy-fourth in the smaller 
specimen. 
Length of larger specimen, 82 mm.; width, including parapodia 
and setae, 12 mm.; without setae, 10 mm. ; without parapodia, 5 
mm. Length of smaller specimen, 61 mm.; width, including para¬ 
podia and setae, 8 mm.; without setae, 6 mm. ; without parapodia, 
2 mm. 
This interesting Polynoid is represented by two specimens in the 
collections, one obtained by Harrington and stated by him to be 
commensal in the tube of the largest species of “ Amphitrite ” found 
by the Expedition, — undoubtedly Thelepus crispus (see p. 428); 
the other collected by Miss Robertson at Alki Point. The latter is 
smaller and evidently younger than the former. The dimensions 
given in the diagnostic description show clearly the difference in the 
proportions of young and old. 
The nearly colorless condition, as well as the great length of the 
body and the thin, translucent, smooth elytra, indicates plainly its 
constantly commensal habit. Forms like P. insignis, P. calif or - 
nica 3 and Harmothoe imbricata , which are sometimes free-living, 
sometimes commensal, retain the pigment, often in heightened inten¬ 
sity, when they have either temporarily or permanently adopted the 
latter mode of life. 
In spite of the excessive number of somites and elytra, the true 
relationship of this form is with the species grouped under the 
genus Harmothoe (sensa extensiori ), and not with Polynoe , where 
numerous somites are much more frequent. The relationship with 
Harmothoe is shown (1) by the structure of the prostomium, (2) 
by the finger-like processes of the rami of the parapodia, and (3) 
by the sequence of the elytra from the 23d to the 32d somite 
(23, 26, 29, 32). A fourth character of less importance is the sparse 
papillation of the cirri — a feature almost invariably present in Har- 
mothoe , and absent in Polynoe. The excessive number of somites 
and pairs of elytra possessed by not a few commensalistic or parasitic 
Polvnoids is no doubt correlated with their mode of life ; hence the 
unusual length attained by the commensal Harmothoe tuta need not 
surprise us, although such a length, and elytra in excess of 15 pairs, 
seem to be as rare in this genus as they are common in Polynoe. 
1 Synonym for P. reticulata Johnson which name is preoccupied by P. reticulata 
Clapar&de. 
