94 DISCOPHOR^. Part III. 



Avlien the lobes are bent downwards (see the same figures as above). The fes- 

 toon-Hke arches, or broken lines, within the deep emarginations, on the contrary, 

 correspond to a thinning of the disk, forming, therefore, arch-like depressions, 

 while the sj^aces along the short junctions, and along the scoojied excavfitions above 

 the ocular apparatus, are somewhat flattened. These bulgings and depressions form, 

 in their combinations, the various irregularities which may be noticed upon the 

 surface of the disk ; they are, however, so slight that they may easily be over- 

 looked. And yet, when the animal emerges upon the surface of the water, and 

 the disk is slightly raised above its surface, spreading uniformly in every direction, 

 and the light shines obliquely ujaon it, it is easy to see how the centre, which 

 corresponds to the inner circle, is slightly depressed, and how that depression is 

 surrounded by a circular wall, corresponding to the periphery of the inner circle, 

 and how, again, the sixteen bulging masses of jelly separate sixteen unequal depres- 

 sions, extending radiatingly from that circular wall towards the thinner edge, the 

 inequality in width of these depressions arising from the circumstance that the 

 more prominent parts of these bulging ridges follow the direction of the crooked 

 lines, and are therefore nearer the long junctions than the short junctions. These 

 unequal depressions are further limited towards the circumference of the disk, on 

 one hand, by the festoon-like depressions in front of the short junctions, and this is 

 the case for the wider depressions ; and, on the other hand, by the scooped depression 

 above the ocular apjjaratus, and this is the case for the narrower depi'essions. 

 When, however, the disk is active, and, bending downward, bulges as a Avhole, 

 dn the shape of a gelatinous balloon, all these inequalities vanish almost entirely 

 in a uniform hemispherical surface, with scalloped edges. 



Between the lower surface of the disk and the floor from which the appen- 

 dages of the lower surface are suspended, there is a wide cavity, divided into a 

 number of chambers, radiating from a common central sjmce to the circumference, 

 where they terminate in numerous minute ramifications. But of this more pres- 

 ently. When the lower floor and all its appendages ai'e removed from the lower 

 surface of the disk (see PI. IV. Fifj. 1, in which a part of these organs is removed, 

 in segments a and «'), all its inequalities are at once brought ^prominently into sight. 

 In the centre there appears a flat, circular space, divided by colorless furrows into 

 a number of unequal, irregular field.s, the larger of which, however, are on the 

 periphery of the circle, their defining outlines alternating more or less regularly 

 with the radiating furrows outside of the circle. The circle itself is defined by 

 a rather deejier circular furrow, also colorless. Following the short («') and the 

 long (o) junctions, there appear sixteen deep furrows, the outlines of which, on a 

 section, have the form of spherical triangles, more acute and deejjer along the long 

 junctions (PL V". F'kj. 3, o'), more open and shallower along the short junctions 



