The Journal of experimental zoology . he bands that leadfrom the sense body to the swimming- „l^ _ I^J • ^L ^ Aboral view of Mnemiopsis leidyi. plates are ciliated, as in other cteno- The four subsagittal rows of phoreS, and, as SamaSSa (92, p. 229) plates, two from each lobe, and the hi r ^1 1 u ^ r _ four subtransverse ones converge on the as shown for other lobate forms, a sense body at the ahoral pole. band of cilia connects plate with plate. In this species, however, the spaces between the plates seem tobe much more sparsely provided with cilia than in other lobatectenophores, i
The Journal of experimental zoology . he bands that leadfrom the sense body to the swimming- „l^ _ I^J • ^L ^ Aboral view of Mnemiopsis leidyi. plates are ciliated, as in other cteno- The four subsagittal rows of phoreS, and, as SamaSSa (92, p. 229) plates, two from each lobe, and the hi r ^1 1 u ^ r _ four subtransverse ones converge on the as shown for other lobate forms, a sense body at the ahoral pole. band of cilia connects plate with plate. In this species, however, the spaces between the plates seem tobe much more sparsely provided with cilia than in other lobatectenophores, if, in fact, cilia are not sometimes entirely absentfrom these regions. The second species upon which I worked, Pleurobrachiarhododactyla, was of simpler structure than Mnemiopsis. Itbelongs to the Cydippidae and has the typical form of an oblongspheroid. Its eight rows of swimming-plates are of about equallength and can be readily distinguished as subsagittal or sub-transverse only by their relations to other parts in the animals. Fig. 2. 410 G. H. Parker. body. In a specimen of average length, about sixteen millimetres,there were approximately 40 plates in each row. Physiological. The resting position of the swimming-plates in both Mnemiop-sis and Pleurobrachia is one in which the individual plate is turnedclose to the body of the animal and with its tip directedorally. In action the plate makes a vigorous stroke aborally andthen returns to its resting position. In consequence of suchmovements carried out more or less simultaneously by certainplates in each row, the animals body is moved through the w^aterwith the mouth forw^ard. The plates in any one row strike oneafter another beginning at the aboral end, /. e., to use the termproposed by Verworn (90, p. 152), they beat the first plate to strike is the most aboral one and theothers follow in sequence giving rise, by the order of their beat, toa wave-like appearance which progresses, of course, in
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