3o6 DISCOVERY REPORTS 



from each corner of the stomach are equally divergent from the perradial direction, each 

 of them having one lateral branch (Fig. 4). These specimens are 1-2* mm. in diameter 

 and have sixteen tentacles. The basal bulbs of the tentacles opposite the eight mam 

 canals are much larger and more fully developed, having more pigment and deeper m 

 colour, than those opposite the branches. The tentacles are also longer and thicker. 



Br I 



Fig. 4. Willia mutabilis. A slightly older stage, 

 in which the two radial canals leaving each of 

 the four corners of the stomach are equally 

 divergent from the perradial direction, each of 

 them having one lateral branch. 



Fig. 5. WilUamutabilis. The radial canal system 

 of an adult having a stomath with eight lobes. 



The second branch in the radial canal system is very variable in position; it may 

 either come off from the main canal (Fig. 6 A, B, E) or from the first branch (Fig. 6 C, D). 

 Specimens with two branches to each of the eight main radial canals are 2-4 mm. in 

 diameter and have about twenty-four tentacles, some of which may, however, be in a 

 juvenile stage of development. 



The third branch is likewise variable and may either come off from the main canal 

 (Fig. 6 F, H) or from the first branch (Fig. 6 G, I). There are several specimens in 

 which some of the main canals have two branches while others have three ; the number 

 of tentacles varies in accordance herewith. Specimens with three branches to all of the 

 eight main canals are 3-4I mm. in diameter and have about thirty-two tentacles. 



In the largest specimens observed within this group (4-5 mm. wide) the number of 

 branches to the main canals varies from three to five (Fig. 5), but the maximum 

 number of five is never seen in all of the main canals of one individual. The greatest 

 number of canals (main canals -1- branches) reaching the umbrella-margin in specimens 

 with eight main canals, as observed in the present material, is forty-one, and the 

 greatest number of tentacles is likewise forty-one. 



In the young specimens the stomach has only four undivided perradial lobes, two 

 radial canals coming off from the end of each lobe (Figs. 2-4). Later on the lobes 

 become broader (Fig. 7 a), and each of them begins to bifurcate (Fig. 7 b), forming two 



