POLYNOE SQUAMATA. 



205 



single median one. The latter (a), or the 2:)rce^tomial tentacle 

 (" antenne mediane," Milne-Edwards), is similar in structure 

 to an ordinary cirrus. Of the other appendages, the upper 

 one upon each side (supero-lateral prsestomial cirrus, " an- 

 tenne mitoyenne ") also resembles an ordinary cirrus (b) ; but 

 the lower (infero-lateral prsestomial cirrus, " antenne ex- 

 terne ") (b') is much larger, and is capable of extreme elon- 



FiG. 5S.—Pol7jnoe sqnamafa. 



A. Posterior extremity from above : c, notopodial cirrus of last somite; d, pygidial 

 cirri ; x, anus. 



B. Anterior extremity from above : a, prsestomial tentacle ; b, superior and b' 

 .inferior prasstomial cirrus ; c, c', notopodial and neuropudial cirri ; e, peduncle 

 of first elytron ; L prsestomium ; /«, parapodium of pcrlstomium. C. Inferior 

 view of anierior extremity, letters as before. 



gation and contraction,* while the ordinary cirri are merely 

 flexible. Altliough at first sight probable, yet it would ap- 

 pear, from Max Muller's account of the development of Poly- 

 noe^ that these two appendages do not, like the two peristo- 

 mial cirri which they essentially resemble, correspond with 

 the notopodial and neuropodial cirri of a single parapodium, 

 inasmuch as they arise from perfectly distinct portions of the 

 pra^stomium. It is very possible that each represents the 

 appendage of a somite, and in this case the praestomium 

 w^ould be composed of at least two somites. Whether the 

 prsestomial tentacle indicates another, or w'hether it is merely 



* I have never o"b*;er\-ed any invagination such as is stated to occur bv 

 Audouin and Milne-Edwards, 1834. (" Histoire Naturelle du Littoral de la 

 France," p. 10.) 



