BY WIILIAM A. HASWELL, M.A., B.SC. 257 



Ehlers* in his remarks on the genus Polynoe states his opinion 

 that Williams had seen the segmental organs of that annelide 

 only imperfectly and the stages in the formation of the sexual 

 products not at all.f A careful examination of the subject has 

 led me to the conclusion that both of these observers were look- 

 ing at the same thing from dijfferent points of view, but were 

 entirely in error in regarding it as the segmental organ. 



At ftrst sight the accounts of the organs in question given 

 by these two observers seem entirely irreconcilable. Williams's 

 description of them is as follows: — ** They appear under the 

 character of pyriform tubuli commencing or ending in a single 

 external orifice. Internally they are lined by a ciliated epithelium, 

 the cilia being large, dense, and acting with great force and 

 vigour. The current raised by these cilia sets up on one side 

 and down on the other. The ciliary epithelium ceases at the 

 point where the primary branches divide. All the rest of the 

 organ is unciliatod and filled with the reproductive products. 

 This part is elaborately branched, — the branches as formerly 

 stated, twining round the diverticula of the stomach. * * ''' 

 The individual tubes are bridled on one side and grandular on 

 the other."+ 



'*The author thinks it probable that if the roots or attached 

 ends of these organs could only be followed through the integu- 

 ments to their extreme outlets they would be found to divide 

 into two limbs, an ingoing and an outgoing; a fact which would 

 account for the clearly divided ciliary currents as they are seen 

 in the dilated portions of the organs. If this fact of the bifurca- 

 tion of the tube were clearly determined, there would be no 

 difficulty whatever in connecting the segmental organs of 



* Die Borstenwurmer, p. 107. 

 t The words are " Ich zweifle nicht dass Williams die Segmentalorgane 

 nur unvollstandig, die Bildungsstatte der Geschlechsproducte iiberhauptgar 

 nicht gesehen hat." 



X " On the Segmental Organs of Annelids/' Phil. Trans. 1358. 



