NOTE ON A SPECIES OF " LUCERNARIA " FROM JAPAN. 69 



bent at a right angle in the middle. They lie respectively inside the 

 four L-shaped ridges which we observed in the external investigation of 

 the calyx. 



The body-wall (Fig. 2, h) consists of three layers, the ectoderm, the 

 entoderm and the supporting layer (Fig. 3, ect., ent., and vies.). The ecto- 

 derm covers all the outer surface of the body. The entoderm lines the 

 coelenteric cavity everywhere. The supporting layer, which is gelatinous 

 and transparent, is found between the above two in every part of the 

 body. Even the wall of the tentacular processes at the tip of the arms 

 shows all these three layers very distinctly. As represented in figs. 3, 6, 

 7, and 8 the genital glands {g) lie between the entoderm and the 

 supporting layer. 



The cavity of the body extends also into the stalk. It is one- 

 chambered on the whole, although at the periphery its cavity is divided 

 into for parts by four very conspicuous ridges running from the calyx to 

 the base. Fig. 4, representing a cross section of the stalk shows most 

 clearly the shape of the ridges (r) as well as the extent of the internal 

 cavity (c). 



The muscular fibres which are found in the supporting layer 

 are grouped into eight cord-like bands, each extending from one tuft of 

 tentacles to the adjoining one. As might be judged from the shape of 

 the cross, these muscular bands are bj^ no means of equal length ; 

 those joining the tufts at the end of the same arm are very short, while 

 others, which extend from the tip of one arm to the tip of the next one, 

 are comparatively very long. 



With regard to the orientation of the animal, we come, by com- 

 parison with other Lucernarice, to the following conclusions : 



1. The radii on which the septa in the arms are found are 

 Interradii, the small opening in the septa in the arms representing the 

 marginal canal of the Acalephce. 2. The tufts of tentacles are con- 

 sequently on the Adradii. 3. The cross shape of the calyx of this 

 medusa is caused by the suppression of growth at the Perradii (compare 

 figs. 2 and 5). 



