276 J. H. ASHWORTH. 



parapoclia of Ophelia limacina; and Rutlike (1843, p. 202, 

 and Tab. x, fig. 15 ; p. 203, and Tab. xi, fig. 14) has de- 

 scribed small apertui'es similarly situated in Ammotrypane 

 oestroides and in A. (= Oplielia) limaciua. He believes 

 these to be ovipores. 



The papilla figured by Theel (1879, pi. iii, fig. 462°) 

 between the notopodium and neuropodium of Euraenia 

 longisetosa is almost certainly a sense organ. There are, 

 in some specimens of Arenicola cristata (Gamble and 

 Ashworth, 1900, p. 443, and pi. 24, fig. 33), small papillae, 

 or sometimes depressions, corresponding in position to that 

 of the ^bovedescribed sense organs, but whether these 

 structures in Arenicola are sensory could not be deter- 

 mined, owing to the defective preservation of the specimens 

 examined. 



The Morphology of the Lateral Sense Organs of 



Poly chaeta. 



The morphology of the lateral sense organs of Capiteilidae 

 has been exhaustively treated by Professor Eisig (1887) in 

 his classical monograph of this family of Polych^etes. In the 

 spring of last year, while working in the Zoological Station 

 in Naples, I had the privilege of discussing this question 

 with Professor Eisig", and I am grateful to him for so care- 

 fully explaining to me his views upon this subject. He 

 believes that these sense organs are modified cirri, and bases 

 his conclusions on the following arguments. (1) The known 

 sensoi-y nature of cirri, as indicated by the pi*esence on the 

 cirii of some Polycheetes of fine stiff hairs. (2) If a gradual 

 shortening of a cirrus took place, the free nerve endings 

 would become more and more aggregated at the free pole of 

 the papilla, thus producing an organ of the same shape and 

 general structure as a ^' Seitenorgan." (3) Each of the 

 lateral sense organs of Capitellidse, being situated imme- 

 diately dorsal to the neuropodium, is considered by Eisig as 

 equivalent to the dorsal cirrus of the neuropodium. He 

 turns for confirmation and support to the parapodia of the 



