76 T. KOMAI : STUDIES ON TWO ABERRANT CTENOPHORES 



shows a distinct otolithic mass in the centre of its cavity. The ribs (c) 

 begin directly outside the sense-organ and terminate at the level about 

 the end of two-third the distance from the aboral pole to the margin of 

 the body. Each rib consists of about twenty comb-plates made up of 

 relatively long cilia, whose beating movements can be observed from 

 the surface of the body of the host. From each interradial corner of the 

 entrance into the sense-organ, arises a ciliary tract ("Nerv", Chun, '8o) 

 (fig. 2, cil, /r), which soon divides into two branches and advances to 

 the aboral end of each rib. 



The tentacular apparatus is located on the lateral sides of the 

 body at a position nearly midway between the aboral pole and the 

 margin of the body. It is nearly the same in structure as in cydippid 

 ctenophores, except for the differences that the tentacle-stem (fig, 8, t. 

 si) is represented by a very short stump-like process having no branches 

 altogether, and that the tentacle-sheath is quite shallow as compared 

 with that of those ctenophores. Along and under each rib, shows 

 through a meridional canal {m. c), which is rather broad especially near 

 its oral blind end, where it may exhibit slight lateral expansions — this 

 tendency is especially marked in subtentacular meridional canals. The 

 spaces between the meridional canals are traversed by some fibres, 

 apparently muscular in nature. Beyond the oral end of the tentacular 

 apparatus, may be observed a pharyngeal canal {ph. c) having a narrower 

 calibre than the meridional canals. 



The ventral surface of the body shows conspicuous foldings (fig. ii); 

 the folds are arranged mostly parallel to the margin of the body. At 

 the centre of the surface, exists an opening elongate in the direction 

 perpendicular to the axis of the tentacles. The entire ventral surface is 

 covered with cilia, the ciliation is particularly heavy in the parts sur- 

 rounding the opening. 



In individuals somewhat smaller in size (about 1.5 mm. in dia- 

 meter; fig, 2), the otolithic granules {ot) are situated at the ends of the 

 tentacular axis of the sensory cavity. The comb-plates {c) are about 

 fifteen in number in each rib, and they bear very short cilia. In the 

 tentacular apparatus {t), the stem has not been differentiated as yet. 

 The meridional canals {in. c) are more roomy than in the larger 

 individual and appear as broad sacs. 



In examples still smaller (i mm. in diameter; fig. 3), the aboral 

 sense-organ can hardly be observed from outside, although discernible 

 in sections as a distinct thickening of the epidermis (fig. 15, s), and the 



