. A manual of zoology. Zoology. 246 CWLESTERATA. rule; it is closely similar, even in the most different si^ecies, and can even be lost (Pelagia), while the medusae are always well devel- oped and present great variety of form. The scyphostoma (figs. 100, 11)1) recalls saioerficially Hydra, but is distinguished externally by a small j)erisarcal cup in which the aboral end is placed. Internally there are four longitudinal folds i^rojecting into the gastral cavity and extending from the margin of the mouth to the opposite pole. These septa or fceiiioke appear in cross-section as small folds of e
. A manual of zoology. Zoology. 246 CWLESTERATA. rule; it is closely similar, even in the most different si^ecies, and can even be lost (Pelagia), while the medusae are always well devel- oped and present great variety of form. The scyphostoma (figs. 100, 11)1) recalls saioerficially Hydra, but is distinguished externally by a small j)erisarcal cup in which the aboral end is placed. Internally there are four longitudinal folds i^rojecting into the gastral cavity and extending from the margin of the mouth to the opposite pole. These septa or fceiiioke appear in cross-section as small folds of entoderm supported by a process of the supporting layer. They are important morpholog- ically, since in budding they jiroduce the gastral tentacles (p/iacelhe) of the medusas. Further, they are the first api^earance of the septal system, so strongly developed in the Anthozoa. The acraspedote medusa are large forms (four inches to four feet or more in diameter) with an arched umbrella often of almost cartilaginous consistency. They are distinguished from the crasjje- dotes externally by notches in the margin of the umbrella, dividing •cx^J the periphery into lobes. In the common forms at least eight lobes occur (figs. 192, 193), each notched at its tip, and in the notch the sensory pedicels bearing both ears and eyes and covered by a lappet. Fig. of Cotylorhiza. In SOme (flsf. 193, /. //) the Seu- (After Glaus.) (//, frastral tentacles , , „ t, ' ' / , (phacellas); rk, marginal (sensory) SOry lODCS lOllOW Cach Other, DUt m others the intermediate region is also notched, the sensory pedicels then being found only on careful searcli (fig. lOi). Tentacles, when present, spring from the notches of the intermediate region. The sensory pedicels predicate the position of eight principal radii, of which four are called the perrailii, the four alternating with them the interradii. Adradii are radii lying betA\'een the principal radii. Tlie lobing of the umbrella infiucnees
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1902
