22 T.KOMAI : STUDIES ON TWO ABERRANT CTENOPHORES 



('92), after calling attention to the difficulty of making out the minute 

 condition of that part, has merel\' stated that, the central filament bends 

 itself into the spiral at the spot. Abbott's observation ('07) on the 

 structure of the colloblast almost agrees with mine, but not on the nature 

 of the spheroidal body. He seems to be of opinion that, the body is the 

 cell-nucleus itself that has come from the mother cell. But this seems to 

 be incorrect, since, beyond other facts, the body exhibits staining reaction 

 entirely different from that of an ordinary cell-nucleus, being eosinophilous 

 and not cyanophilous. 



Next I may mention the development of the colloblast, although 

 my observetion on each successive stage is not very satisfactory. As 

 already indicated, the colloblast develops in the distal parts of the basis- 

 epithelium, where the epithelium is made up exclusively of the mother 

 cells of the colloblast in various developmental stages. Each undifferen- 

 tiated mother cell is polygonal in shape and provided with a dispro- 

 portionately large nucleus situated in the centre (PI. 4, fig. 12, a). The 

 development is initiated by a change that consists in the differentiation 

 of two kinds of granules out of the cytoplasm, one, very fine and 

 eosinophilous, and the other, somewhat coarser, hardK' stainable and 

 appearing ver}^ refringent. The former assemble about the nucleus, which 

 has become somewhat eccentric in situation, while the latter occupy the 

 parts of the cell-body opposite to the nucleus (b). The segregation of 

 the two kinds of granules becomes more and more apparent with 

 development, meanwhile the nucleus has grown quite eccentric and 

 located at the margin of the cell-bod_\' (c). Then the first trace of the 

 spiral filament makes its appearance in the neighbourhood of the nucleus. 

 It is like a cord turning spirally a few times (d); no doubt it is derived 

 from the eosinophilous plasmic granules described above. The length of 

 the filament increases with development at the expense of those granules, 

 until finally, seven or eight spiral rings are formed. The refringent 

 granules assemble on the surface of the cell and arrange themselves into 

 the superficial layer. The main part of the cell-body changes into the 

 head of the colloblast. The nucleus remains until a comparatively later 

 period without showing any change whatever. At about the time when 

 most of the rings of the spiral are formed, the nucleus begins to be 

 elongated in the direction of the axis of the spiral. It is spindle-shaped 

 for some time, but finally it is drawn out and becomes filamentous (f, g). 

 Thus it is clear that, a colloblast develops from a single formative cell, 

 the cytoplasm forming the head and the spiral filament, and the nucleus 



