Text-book of comparative anatomy . the purpose of blood-vessels (which are wanting) andconvey food from the centralstomach to the organs at thediscs edge. These two portionsform the peripheral some Craspedote Medn*n;besides the radial canals andthe circumferential canal, theendoderm from the centre tothe circumference persists, itstwo layers being pressed to-gether by the strongly de-veloped oral or subumbrellarand aboral or exumbrellar jelly,thus forming the so - calledvascular lamellae or eatham-mal plates, the layers of which,separating in radial strips, formthe radial canals.
Text-book of comparative anatomy . the purpose of blood-vessels (which are wanting) andconvey food from the centralstomach to the organs at thediscs edge. These two portionsform the peripheral some Craspedote Medn*n;besides the radial canals andthe circumferential canal, theendoderm from the centre tothe circumference persists, itstwo layers being pressed to-gether by the strongly de-veloped oral or subumbrellarand aboral or exumbrellar jelly,thus forming the so - calledvascular lamellae or eatham-mal plates, the layers of which,separating in radial strips, formthe radial canals. The radial canals in simpleMedusa are 4 in number, andare placed cross-wise. Theradii in which they lie arecalled perradii (Fig. 65, A, a-b).In order to define the positionof other tentacles, canals, andorgans, the radii exactly half way between the perradii have been called interradii. Half way between the 4 perradii and the 4 interradii lie the 8 adradii (b-c); half way between the 8 former and the 8 latter lie the 16 FIG. 65. — Eucope campanulata, partly afterHaeckel A, From the surface. B, Section in thedirection a-b-c in Fig. A. a-b, Perradius; b-c, ad-radius ; t, tentacle ; sb, marginal vesicle; g, gonades ;mr, gastric peduncle; r, radial canals; i; velum ;ri, circumferential canal; ex, exumbrella ; su, sub-umbrella ; gn, jelly; tg, tentacular vessel; b-b, mainaxis. ii GNIDARIA—GENERAL 75 From the margin of the disc a thin muscular membrane projectsinto the subumbrellar cavity like a diaphragm ; it is known as theVelum (r), and is one of the principal locomotory organs of theCraspedote Medusce. There are many other organs at the margin of the disc, the princi-pal being: 1. A double nerve ring. 2. Marginal vesicles. 3. Eye spots. 4. A ring of nematoeysts. We shall speak of these organs later on. The derivation of the Medusa form from the Hydropolyp is themore probable as Medusce belonging to many divisions, in their in-dividual development, proceed from Hydr
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
