brilliant than that of the Pleurobrachia. The Bolina, with its slow, undulating motion, its broad lobes sometimes spreading widely, at other times folded over the mouth, its delicacy of tint and texture, and its rows of vibrating fringes along the surface, is nevertheless a very beautiful object, and well rewards the extreme care without which it dies at once in confinement. _Idyia_. (_Idyia roseola_ AG.) [Illustration: Fig. 33. Idyia roseola seen from the broad side, half natural size; _a_ anal opening, _b_ lateral tube, _c_ circular tube, _d_ _e_ _f_ _g_ _h_ rows of locomotive flappers. (_Agassiz_.)] The lowest genus of Ctenophoræ found on our coast, the Idyia (Fig. 33), has neither the tentacles of the Pleurobrachia, nor the lobes of the Bolina. It is a simple ovate sphere, the interior of which is almost entirely occupied by an immense digestive cavity. It would seem that the reception and digestion of food is intended to be the almost exclusive function of this animal, for it has a mouth whose ample dimensions correspond with its capacious stomach. Instead of the longitudinal split serving as a mouth, in the Bolina and Pleurobrachia, one end of the body in the Idyia is completely open (Fig. 33), so that occasionally some unsuspicious victim of smaller diameter than itself may be seen to swim into this wide portal, when suddenly the door closes behind him with a quick contraction, and he finds himself a prisoner. The Idyia does not always obtain its food after this indolent fashion however, for it often attacks a Bolina or Pleurobrachia as large or even larger than itself, when it extends its mouth to the utmost, slowly overlapping the prey it is trying to swallow by frequent and repeated contractions, and even cutting off by the same process such portions as cannot be forced into the digestive cavity.