Zool.— Vol. I.] JOHNSON—PACIFIC COAST ANNELIDS. 169 



of being the first marine Annelid from the California coast 

 described in any scientific work. A brief Latin diagnosis 

 of the species was given by Kinberg in 1855 1 and a more 

 ample description, with several fairly good figures, in the 

 " Eugenies Resa " in 1858 2 . 



In this second account Kinberg states that his specimens 

 were obtained at " Sausalito Bay, near San Francisco, Cali- 

 fornia, on the shore and at a depth of eight to ten fathoms." 



Probably no species of this great family, noted for the 

 morphologic plasticity of many of its members 3 , is more 

 variable than this. The variation it exhibits is unquestion- 

 ably due to differences in its environment. It is not only 

 free-living under a variety of conditions (under stones, 

 among tunicates, mussels, sea-weeds, etc.), but is also a 

 common commensal in the tubes of species of Amphitrite 

 and Thelepus. Like another tube-commensal of our coast, 

 Polynoe reticulata, it attains a larger size in this mode of 

 existence than when free-living, but not unless it lives in a 

 tube of liberal dimensions, so that both the rightful occupant 

 and its messmate have ample space. As with other species 

 of the genus, there is a strong tendency for the commensal to 

 attain a great length, and but slight proportionate diameter. 

 This condition is probably seen at its maximum in Polynoe 

 ocellata of Japan (commensal with the narrow-tubed Spio- 

 chcetopterus challenger ice*), which, according to M'Intosh 4 , 

 has over 100 somites, more than 50 pairs of 

 elytra, measures 60 mm. in length, and only 2.5 mm. in 

 width, including the setae. Not alone are the commensal 

 individuals of the present species longer and proportionately 

 narrower than the free-living ones, but they exhibit other 

 peculiarities. The elytra are thinner, smoother, sometimes 

 destitute of any except microscopic tubercles, with few or no 

 marginal "cilia," and not so likely to extend to the extreme 

 posterior end of the body, reaching usually not further back 

 than the anus. There is a marked tendency to develop a 



»1. c, p. 385. 



»1. c, p. 18, Taf. V, figs. 25 a-h. 



3 For an excellent account of the variability of Polynoe so»amataand P. clava, see Bourne 

 "Certain Points in the Anatomy of the Polynoina", Trans. I.iun. Soc. (London) 

 2nd Ser., Zoology, Vol. II, pp. 347-356, Pis. XXXIV-XXXVI. 



^Challenger Reports, Zoology, Vol. XII, p. 126, PI. XII, fig. 3. 



