i6 T. KOMAI : .STUDIES ON TWO AIJERRANT CTENOPHORES 



In PI. 4, fig. 8 is .shown somewhat diagammatically the structure 

 of the aboral region of C bocki in the retracted state, the figure repre.sen- 

 ting the section of the region along the sagittal plane of the body. A 

 prominent folding of tissues occurs below the general level of the 

 epidermis above the sensory capsule. At the entrance into the capsule, 

 one can recognize a thickening of the epidermis to be identified as the 

 peripheral part of the marginal area of the polar plate. Below this part 

 occurs a very thin ciliated epithelium, which constructs the central area 

 of the plate {c. a); abundance of sphincter fibres (sp/i) are found in the 

 parenchyme tissue directly adjoining this part. Next exists a thickening 

 of the epithelium, which forms the proximal part of the marginal 

 area of the polar plate. 



The sensory capsule is apjiroximately spherical in form, its wall is 

 made up of slender ciliated cells. Owing to the topographical differences 

 shown by these cells, one can distinguish some zones in the capsular 

 wall: — Directly succeeding downwards the part constructing the proximal 

 margin of the polar plate, is a zone carrying very long cilia (cu). The 

 cilia appear to be cemented together by a material staining vividly with 

 eosin. Without doubt, the cilia represent the cupule of the sensory 

 capsule of ordinary ctenophores, although they are never found to fuse 

 together so firmly as in those forms. The cells bearing them are roughly 

 columnar in shape and the cytoplasm stains with eosin somewhat better 

 than that of the cells in the neighbouring zones. 



Below the zone mentioned above, the wall of the capsule is con- 

 structed for the greater part by very tall and slender cells carrying short 

 cilia. The nuclei are situated in the wall in three to six strata. Near the 

 bottom of the capsule, exists a zone of cells containing highly acidophil- 

 ous granules {g-. o-y The granules are apparently the same that are 

 observed to form the greenish pattern referred to before. In this same 

 zone or perhaps below it occur cells which carry the cilia supporting 

 the otolithic mass (da/). The cilia arc distributed evenly on all sides of 

 the capsular wall without fusing into "balancers" as in ordinary cteno- 

 phores. To each otolithic granule is attached a nucleus which cotnes 

 from the mother cell of the granule. 



As it is evident from the above description, the ab(>ral sense-organ 

 of Coeloplana may be said to be nearly identical in every point with 

 that of ordinary ctenophores. But, it shows clearl)- the signs of degenera- 

 tion as regards some features, as for instance, diffuse cilia instead of the 

 balancers and also the rudimentai)' condilion of the polar plates. 



