34 



9. Organs of secretion. 



Under this category may be reckoned a rather voluminous and according to its whole 

 structure exquisite glandular apparatus (Tab. II, fig. 8fg) which has its place in the middle, 

 immediately above the roof of the stomach between it and the dorsal skin of the disc. The 

 apparatus, which evidently enough corresponds according to its situation to the so-called 

 interradial caeca or rectal caeca in other star-fishes, consists of 2 unequal parts united in the 

 middle, of which one is usually twice as large as the other. Their arrangement is always 

 constant, so that the smaller section turns to that side of the periphery where the madre- 

 poric body is situated, but their size varies in different individuals. In the middle,, where 

 both sections unite, the whole apparatus is attached by a ligament, as well to the roof of 

 the stomach as to the inside of the dorsal cuticle, on which the ligament is continued in 

 the form of 2 thickened stripes proceeding from the centre in different directions, and then 

 both curving towards one side of the periphery, uniting themselves each with one of the 

 longitudinal ligaments by which the 2 radial caeca situated nearest on the right of the madre- 

 poric body are attached (see Tab. VI, fig. 6). The central part of the ligament is perfo- 

 rated by a narrow canal, the excretory passage, which ascends and has its issue on the 

 dorsal side of the disc in a fine pore surrounded by a somewhat raised elliptical border 

 (Tab. I, fig. 1 a). Although the point where the ligament is attached to the inside of the 

 dorsal skin lies exactly in the centre, it will always be found that the said pore has an 

 evidently excentric position, being always found nearer to that side of the periphery where 

 the madreporic body has its place (see Tab. I, "fig. 3, 4 a, Tab. II, fig. 1, 2). This is caused 

 by the excretory passage perforating the thick dorsal skin in a very oblique direction, which 

 also quite naturally accounts for the peculiar elliptical form of this pore (Tab. I, fig. 7 a). 



With respect to the structure of the apparatus in question, it seems to be, as be- 

 fore mentioned, completely glandulous. Both the main parts which compose the apparatus 

 consist of a rather firm and compact mass externally divided into a greater or less number 

 of large irregular lobes, and each of these lobes again into a great number of smaller 

 rounded lobules, whereby the whole apparatus acquires the appearance of a real acinous gland. 

 On the outside there is a thin but tolerably resistent membrane, wherein there may be seen, 

 more or less distinctly, various fibres that partly cross each other (muscular fibres), and in- 

 side an opaque white granular substance, which on the side where both sections meet 

 appears more loose and transparent. The whole apparatus rests immediately on the roof of 

 the stomach, but so that a greater or smaller part of the latter always remains uncovered 

 (see Tab. II, tig. 8). 



