POLYNOE SQUAMATA. 



205 



single median one. The latter (a), or the prcestomial 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 prcestomial cirrus, " an- 

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

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

 terna ") {b') is much larger, and is capable of extreme elon- 



Fig. bZ.—Polynoe squamata. 



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

 cirri ; x, anus. 



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

 inferior prsestomial cirrus ; c, c', notopodial and neuropodial cirri ; e, peduncle 

 of first elytron ; I, praestomium ; m, parapodiura of peristomium. C. Inferior 

 view of anterior extremity, letters as before. 



gation and contraction,^ while the ordinary cirri are merely 

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

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

 noey 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 

 praestomium. It is very possible that each represents the 

 appendage of a somite, and in this case the praestomium 

 would be composed of at least two somites. Whether the 

 prsestomial tentacle indicates another, or whether it is merely 



1 1 have never observed any invagination sucli as is stated to occur by 

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

 France," p. 10.) 



