LAMELLISABELLA JOHANSSONI 



433 



of a succession of segments each 

 bearing on its front edge a barely per- 

 ceptible, narrow membranous frill or 

 collar. The length of a segment is just 

 a little less than the diameter of the 

 tube (Fig. 168). In general the tube 

 strongly recalls that of Polybrachia an- 

 nulata, but it is distinguished from it 

 by the weakly developed frills of the 

 segmental margins. The mouth of the 

 tube is a broad thick-walled funnel 

 (Fig. 168/i). Amongst a large number 

 of fragments of tubes a few were found 

 with two to five such funnels developed 

 not far from each other near the front 

 end of the tube (Fig. 168,5, C). It is not 

 known how far this appearance may be 

 considered normal. We may suppose 

 that the function of the mouth of the 

 tube, as shown in Fig. 1685, is served 

 at first by the lowest funnel. Then the 

 tube has increased in length by re- 

 newed growth and completed a new 

 funnel-like mouth. Following this, 

 after renewed growth of the tube, yet 

 another funnel has been formed, and 

 yet more. Finally after the formation 

 of five funnels, subsequent growth has 

 occurred in a different manner, by 

 means of the deposition of new layers 

 of tube material on the inner surface of 

 the oral funnel, forming a multiple 

 funnel. It is possible, however, that the 

 whole series of funnels was formed in a 

 continuous operation, without inter- 

 ruption, while the tube was growing 

 in length. Some such mechanism as 

 this must be invoked to account for the 

 front end of the tube illustrated in 



Ш 



Fig. 168. Lamellisabella johanssoni: 

 Tube : A - front end ; В - front end 

 with supplementary funnels; С - 

 the same under higher magnification. 

 (After Ivanov, 1957a.) 



