lo T. KOMAT : STUDIES ON TWO ABERRANT CTENOPHORES 



shape, but generally takes an oblong shape when contracted. At the 

 centre of the dorsal surface, lies the aboral sense-organ (PL 2, figs, i & 

 4, s); directly below it and on the ventral surface, is situated the mouth 

 (;;?'). The two organs just mentioned determine the main axis of the 

 body. The vertical plane determined by this axis and by either the 

 long or the short diameter of the oblong body may be called the 

 "perradial" planes, of which one is the "transverse" or "tentacular" 

 plane and the other the "sagittal" or "pharyngeal" plane, distinguished 

 according to their including the long or the short body-diameter re- 

 spectively. The two planes intermediate between the perradial planes 

 and forming with these an angle of 45° may be called the " interradial " 

 planes. 



The tentacular apparatuses (/), which lie in the tentacular plane, 

 are nearly identical in structure with those of cydippid ctenophores, 

 excepting for the fact that, both the tentacle-basis (/. d) and the tentacle- 

 sheath (a s/i) are placed horizontally instead of vertically as in those forms. 

 The mouth leads dorsal ly into a spacious pharynx (//^') of a depressed 

 form, which is succeeded dorsally by the oesophagus (oc) shaped like 

 a compressed tube. Both the pharynx and the oesophagus are clothed 

 with an epithelium of ectodermal origin. The oesophagus opens aborally 

 into the infundibulum (i) situated immediately beneath the sense-organ 

 and forming the centre of the entire canal-system. The canal-system is 

 arranged essentially in the same way as in ordinary ctenophores : — A 

 pair of perradial canals (figs. 2 & 4, per. c) proceed from the transverse 

 wall of the infundibulum, and each of them divides at once into three 

 branches, of which the lateral two (s. ph. c) represent the subpharyngeal 

 meridional canals of ordinary ctenophores and the median (A c) the 

 trunk of tentacular canals. This latter soon divides into two branches 

 which accompany the tentacular apparatus on its ventral side. Each of 

 these two branches gives rise dorsally to a canal (s. t. c) which represents 

 the subtentacular meridional canal of ordinary ctenophores; the canal runs 

 nearly parallel to the transverse axis of the body along either side of the 

 tentacle-sheath. All the canals mentioned above, excepting the perradial, 

 give rise to several branchlets that divide and anastomose and bring about 

 the extensive canalar network of the peripheral parts of the body {br. c). 

 The infundibulum further sends out from either of its sagittal sides a 

 narrow canal, the "excretory" canal {ex. c), which proceeds dorsally to 

 open externally without dividing unlike the same of ordinary ctenophores. 

 The gonads develop from the dorsal wall of the eight canals representing 



