Notes on the Adult Anatomy of Solaster encleca. 183 



(3) Dissection of Adidt Specimens. 



The muscular bands which run in the middle line of each ray along the 

 inner aspect of the aboral wall and meet in a knot at the centre of the disc 

 form, perhaps, the most definite and satisfactory guides for locating the 

 position of the anus. On careful dissection, it will be seen that the anus 

 occupies a bay slightly to one side of the centre of the knot, the bay being 

 formed by the divergence from the knot of the radiating muscular bands 

 belonging to rays V. and VI. Two specimens of Solaster endeca (one with 

 eight and the other with nine rays), and three specimens of S. papposa (with 



V 



VI 



vn 



w 



til y^ 





T 



_ft. 

 _ck 



tm 



Fig. 6. 



The central part of the aboral body wall of a large S. papposa seen from the deep aspect 

 and illustrating position of anus. 



c. k. . central knot of aboral musculature continued orally as a short band passing 



to the commencement of the rectum. 

 /. 6. . fibrous band passing from commencement of rectum outwards to join radial 



muscle of ray V. 

 I., II., III., etc. the various mid-radial lines. The madreporic interradius is I., II. 

 r. m. . the aboral muscular bands of the various rays. 

 rt. . rectum. 



ten, thirteen and fifteen rays respectively) showed this condition, which 

 may accordingly be taken as the normal one for the Solasters no matter what 

 may be the number of rays in the individual or in the species (see Fig. 6). 



In an ordinary starfish the anus lies in interradius V./VL, according to 

 the method of numbering previously indicated. In my paper on the develop- 

 ment of Solaster endeca (8), I have shown that the sequence in appearance of 



