22 ANNELIDS. I. 



sides, are straight and pointed. The ventral setae, which arc arranged flabellately and are most 

 delieate in shape, almost capillary, form together an excellent swimming organ. Mc. Intosh coni- 

 i s the aspect of a dorsal bristle with the stem of an Eqnisetnm, considering the collars composed of 

 the spines of the former as resembling the connate leaves of the named plant. The likeness is reallv 

 lather striking. Another circumstance, not mentioned by Mc. Intosh, is that the bristles are hollow, 

 a fact which likely is related to the pelagic behaviour of the animal; they are exceedinglv fragile and in 

 preparations of parapods I have often seen the broken bristles filled with air. 



One of the most peculiar features in the animal is the organ indicated by Mc. Intosh as the 

 "caudal rudder 1 ." It forms a backwards directed rod. on the ventral side of which is situated a 

 longitudinal membrane; along the dorsal side of the rod is found a lower membrane which, however, 

 is exceedingly delicate and transparent, so that it is difficult to perceive. 



Harmothoe badia Theel. 



1878. Polynoe badia, Theel: Kgl. Sv. Vet. Akad. Handl. Vol. XVI, p. 18. 



1883. , Wiren: Vega Exped. II, p. 390. 



1886. Harmothor badia, Levinsen: Kara-Havets Ledorme p. 3. 



1909. , Hj. Ditlevsen : Annal. polych. p. s- 



Localitv : 



The Iugolf-Exped. St. 38. 59°i2' N. L,. 5i°05' W. L. 1870 fms. Southern part of the Davis Strait. 



— - 104. 66°23' 7°25' 957 — East of Iceland. 



- 105. 6 5 °34' - 7°3i' — 762 — - - 



- no. 66°44' — ii°33' — 781 — — 



- in. 67°i4' 8°48' — 860 — North East of Iceland. 



- 116. 70°05' 8°26' 371 — South of Jan Mayen. 



- 117. 69°i3' — 8°23' — 1003 — — - 



- 118. 68°27' 8°20' — 1060 — — 



- 119. 67°53' — io°i9' — 1010 — North East of Iceland. 



- 120. 67°29' — n°32' — 885 — — - 



- 140. 63°29' 6°57' — 780 — North of the Faroe Islands. 



1 Since the completion of my manuscript a new paper lias been published by P. Fauvel lAunelides polvchetes pelagi- 

 ques provenant des campagnes des yachts Hirondelle et Princesse-Alice 11S85 — 1910), Monaco 1916). Iu this treatise the author 

 discusses the named organ and the morphology of the same. He describes thoroughly its anatomical structure and communi- 

 cates .in far as possible its physiology, but as to its origin and morphological value his investigations give no positive result; 

 all that he says in this respect is negative. 



According to my opinion the organ under consideration is formed by the latest, strongly transformed parapodium 

 on the left side. I must confess that for the present I am not able to prove this, but a preparation of mine gave me the 

 idea (PI II, fig. 6). which after a re-examination, I, find very likely. One of the most caudal situated parapodia on the same 

 side proves namely a resembling transformation, only in a much lesser degree; on the ventral side of its stem is seen a mem- 

 brane running longitudinally from the base of the foot towards the tip; it is not difficult to imagine this transformation 

 increasing to such a degree that the result must be the "caudal rudder." In the interest of the truth I must confess, that I 

 have not been able to state the feature here described as constant. The fig. n, PI. II has been painted after a small specimen, 

 the hindpart of which has been cut off, then cleared in Glycerine and afterwards kept on a slide in Gelatine Glycerine 



