STRITCTURE AND DEVFJ.OPMENT OF COF.LOl'LANA. 21 



All the accessory filaments are covered all over by colloblasts. 

 These are apparentl}' the same in structure as those of ordinary cteno- 

 phores. But as the descriptions on the structure of previous writers 

 seem to be unsatisfactory, I shall deal with it in some length. 



The colloblast or the adhesive cell (PI. 5, fig. 12, g) consists of a 

 bell-shaped main part which may be simply termed the head (Ji) and 

 two accessory filamentous bodies, one spiral {s. f) and the other nearly 

 straight {c. f), attached to the concave side of the head. The head is 

 made up of a substance which stains fairly well with eosin. The convex 

 surface is coverd by refringent granules {gr) arranged in one layer, to 

 which the .sticky nature peculiar to the colloblast is probably to be 

 attributed. Directly beneath this layer is found another of small spherules 

 {sphl) arranged at fairly regular intervals from one another. They 

 present somewhat higher eosinophily than the surrounding ground 

 substance. A spheroidal body {c. spJi) is situated nearly in the centre 

 of the head. It takes up eosin as strongly as the spherules mentioned 

 above. Some delicate fibrous tracts radiate from that body through the 

 substance of the head. Besides, two filaments are connected with the 

 body. One of them, the spiral filament {^s. f), is of muscular nature, 

 staining with eosin fairly well. The spiral makes seven or eight dextral 

 turns around the other filament, vvhich is to be called the central filament. 

 This {c. f) is much finer than the spiral filament and passes almost 

 directly through the axis of the coil of the latter. It is attached to the 

 base of the spheroidal body in the head already described at the distal 

 end, and to the external membraneous covering of the accessory tentacle 

 at the proximal end. The spiral filament joins the central filament just 

 at, or a little above this latter point of attachment. The central filament 

 stains with haematoxylin very well, which character distinguishes it 

 sharply from the spiral filament. 



It is a rather remarkable fact that the existence of the central 

 filamant of the colloblast is not mentioned in the works of such authors, 

 as Chun ('80) and Schneider ('02). According to Delage and Herouard 

 ('01), its presence had been denied by Vignon. Hertwing ('80), Samassa 

 ('92) and Abbott ('07), however, have noticed the existence of the 

 filament definitely. Chun's figures show ('80, PI. 18, figs. 6, 10 and 12) 

 the spiral filament attached directly to the granular layer on the surface 

 of the head, while Hertwig ('80) has pointed out the presence of a 

 "Korn" at the centre of the latter, whence proceeds the spiral filament, 

 referring undoubtedly to the spheroidal body described above. Samassa 



