Interradial sentence example
Usually the four subgenital cavities are distinct from each other (so-called tetrademnic condition), but in many Rhizostomeae, for example, Crambessa, the subgenital cavities join together under the subumbral floor of the stomach (so-called monodemnic condition) and coalesce to form a so-called subgenital portico placed on the oral side of the stomach, opening by four interradial apertures between the oral arms, that is to say, by the four primitive apertures of the subgenital pits.
Interradial tentacles may be also developed, so that the total number present may be increased to eight or to an indefinitely large number.
The four sub-genital pits are seen to be interradial.
The eight adradial gonads on the subumbral walls of the four radial pouches, representing primitively four horse-shoeshaped gonads each divided into two by an interradial septum.
The four gastric interradial ridges are seen through the mouth.Advertisement
The sixteen tentacles of the scyphistoma disappear, and in the place of the four perradial and four interradial tentacles, the eight tentaculocysts of the adult are formed as outgrowths of the subumbral margin, independently of the tentacles of the scyphistoma (Friedemann).
The ephyra has a flat, disk-shaped body, with eight marginal lobes (four perradial, four interradial); a tentaculocyst is lodged in a deep notch at the apex of each lobe.
As the 1 The four primitive interradial cathammata disappear in the fully formed ephyra and become replaced by sixteen subradial concrescence-areas without any ostia or ring-canal at the margin.
E, Young ephyra just liberated, showing the eight bifurcate arms of the disk ' and the interradial single gastral filaments.
Semon called this stage the Pentactula, and supposed that, in its early history, the class had passed through a similar stage, which he called the Pentactaea, and regarded as the ancestor of all Echinoderms. It has since been proved that the five tentacles with their canals are interradial, so that one can scarcely look on the Pentactula as a primitive stage, while the apparent simplicity of the Synaptidae, at least as compared with other holothurians, is now believed to be the result of regressive vlu.Advertisement
The genital organs in both Asteroidea and Echinoidea would retain the interradial position they first assumed in Edrioaster; and in Echinoidea their primitive temporary openings to the exterior were converted into definite pores, correlated with five interradially placed plates at the aboral pole.
The mesogloea becomes enormously increased in quantity (hence the popular name "jelly-fish"), and in correlation with this the endoderm-layer lining the coelenteron becomes pressed together in the interradial areas and undergoes concrescence, forming a more or less complicated gastrovascular system (see Medusa).
Taking as a starting-point the wide archenteric cavity which the medusa inherits primitively from the antecedent actinula-stage (see article Medusa), we find, in such a form as Tessera, four interradial areas of concrescence between the exumbral and subumbral layers of endoderm, four so-called septal nodes or " cathammata," subdividing the stomach into four wide, radially situated pouches which communicate with each other beyond the septal nodes by wide apertures constituting what is termed by courtesy a ring-canal.
Interradial septal ridges, passing into the taeniolae (f.t) in the stalk.
Primitively there are four perradial tentacles, to which may be added four interradial, or they may become very numerous and are then scattered evenly round the margin, never arranged in tufts or clusters.Advertisement