20 T. KOMAI: STUDIES ON TWO ABERRANT CTENOITIORES 



transverse plane. The formative zone of the accessory filaments is 

 locaHzed at the distal end of the tentacle-root (PI. 3, fig. 8), while that 

 of the tentacle-stem extends all through the remaining parts of the root. 

 The rudiments of the muscle-fibre appear at first as a gelatinous mass 

 stained uniformly {m. /'); the fibrous character becomes apparent only 

 in a later stage with development {in f). The fibres show at first 

 basophily, but acidophily afterwards. 



As is indicated above, the accessory filaments (PI. 3, figs. 6, 8: a. 

 f) develop from the distal end of the tentacle-root and are transferred 

 gradually towards the stem with which they are connected at last (fig. 

 8). Each of them at first shows numerous nuclei in it, but no muscular 

 characteristics whatever. Such primordial accessory filaments are found 

 usually in crowd, so that there may appear as many as thirty of them 

 in a single cross-section of the tentacle-root (Fig. 6, a. f). 



The tentacle-stem seems to present nothing peculiar than what is 

 already known in cydippid ctenophores. It consists of a core of longi- 

 tudinal muscle-fibres covered by an epithelium. The interspaces between 

 the fibres are occupied by a gelatinous cementing matter called " Perimy- 

 sin " by Samassa ('92). This contains some nuclei in it, whereas, the 

 fibres do not show them altogether. The entire core is divided into two 

 lateral halves throughout its length by a septal band of gelatinous tissue. 

 This band is directly continuous with the gelatinous tissue that divides 

 the tentacle-root into two lateral halves mentioned already. 



The accessory filaments are attached to the stem on the ventral 

 side, in the same plane as the band. Their structure conforms largely 

 with Aubott's description and figure of the same organ of C. Diitsuktirii 

 ('07, PI. 2, fig. 37). It is roughly cylindrical in form and consists of 

 two kinds of tissues, one muscular and the other gelatinous, the former 

 stains well, the latter only weakly, with acid dyes, and the latter alone 

 contains nuclei in it. The distribution of the two kinds of tissues may 

 be understood from PI. 4, fig. 1 1 (longitudinal section) and fig. 10 

 (transverse section). A narrow slit-like space of the gelatinous tissue 

 occupies the median plane, and on each side of it, occurs another space 

 appearing crescentic in cross-section, outside the latter and close to, and 

 parallel with, the lateral margin is found still another space which is as 

 narrow as the median. The muscular tissue between those spaces is 

 nearly the same in breadth everywhere. The accessory filament is 

 identical in structure in the three species, no structure such as depicted 

 in Acijott's PI. 10, fig. i'$> having been met with. 



