60 AUSTRALASIAN ANTARCTIC EXPEDITION. 



Having once recognised the position of the articulations, one can see a bending 

 of the bristles, forming an open angle, which might be taken for a mere " bend " till 

 the existence of the articulation was ascertained. 



Even when I had satisfied myself of their existence, I found it very difficult to 

 detect these articulations in specimens mounted in glycerine jelly, even by the use of 

 a high power, but it is easy to see them in fresh glycerine. I re-examined specimens 

 mounted in glycerine, twelve months later, and saw the articulations quite clearly in 

 every chaeta. 



The length of the appendix is small, compared with the total length of the bristle. 

 I had some difficulty in estimating what its length is, since the bristle is so long that it 

 will not lie wholly in the field with an objective 3 and ocular 3 of Leitz, and a lower 

 magnification is useless. By a fortunate chance a small air bubble occurred in the 

 preparation about half way along one of the bristles, so that by making two camera 

 drawings I was able to get practically the entire bristle, and was thus able to measure it. 

 The total length is represented in the drawing by 570 mm., and the appendix by 10 mm. 

 approximately, for its tip is so fine that under this magnification it is invisible. Roughly, 

 one may say that the length of the appendix is about -$ of that of the total (fig. 61). 

 It may be noted that Mclntosh says that " none of the extremely attenuate tips are 

 complete." So that there is no real contradiction between his account and that of 

 Willey. It is probable that all the appendices had dropped off or been broken off in 

 the specimen, as is the case in many of the chaetae in those before us. 



(2) The second point is explained, I think, by the fact that Mclntosh had repre- 

 sented in his figure the head from the dorsal aspect, and Willey drew attention to the 

 structure of the ventral aspect, in order to complete the description of the species, 

 as Mclntosh had not given an accurate figure of this surface. 



(3) The third point is, I believe, due to an error in observation by Gravier 

 himself. Willey states that in the everted pharynx the entrance is surrounded by 

 twelve soft conical papillae. In the specimen described by Gravier the pharynx was 

 not everted; he states that it extends backwards as far as the 20th segment, where 

 it is bent upon itself. He goes on to say (p. 68) : " Le bord de 1'orifice posterieur est 

 fronc6, mais ne presente pas ni papille definie, ni prolongements digit if ormes." 



He omits to mention the buccal region. Now, of course, the papillae being at 

 the entrance of the pharynx from the buccal region must be looked for, not at the 

 posterior extremity, but at the anterior extremity of the pharynx when at rest inside 

 the body. 



I dissected the male individual and find that the buccal region is very short, 

 extending to about the 5th or 6th segment, including the peristomium; then follow the 

 long " trompe tres musculeuse," which reaches to the 20th segment; then it bends 

 upon itself and reaches forward to the 15th segment, where it enters the thin- walled 

 intestine. On slitting open this apparatus I find at the anterior extremity of the 

 pharynx or " trompe " the series of papillae described and figured by Willey. 



