. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. 24 DISCOVERY REPORTS The calycophoran condition is best seen in the Prayids and in the Hippopodiids. Here the budding zones arise and remain close to each other, and the increase in length of nectosome and siphosome takes place in opposite directions. This is particularly noticeable in Hippopodiids, where the region adjoining the joint budding zones forms an upper, progressively twisting loop, and the nectosome forms a spiral-shaped, pendant housing (hydroecium) for the siphosome, which hangs do
. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. 24 DISCOVERY REPORTS The calycophoran condition is best seen in the Prayids and in the Hippopodiids. Here the budding zones arise and remain close to each other, and the increase in length of nectosome and siphosome takes place in opposite directions. This is particularly noticeable in Hippopodiids, where the region adjoining the joint budding zones forms an upper, progressively twisting loop, and the nectosome forms a spiral-shaped, pendant housing (hydroecium) for the siphosome, which hangs down inside and is retractable within it. In the early stages of Hippopodiid growth the larval nectophore is attached above the joint growing-zone, but is later cast off. Text-fig. 5. A, larva of Physalia physalis (after Okada, 1932) for comparison with B, larva of Nanomia bijuga, C, young Physophora hydrostatica (diagrammatic) after elongation of nectosome, and D, adult Athorybia rosacea (diagrammatic), E, diagrammatic ventral view of D to show the succession of gastrozooids. In all four species there is a terminal protosiphon Gz1, one or more secondary gastrozooids in a nearby group and a separate budding zone for the main succession of gastrozooids. Leaving out of account the larval Hippopodiid nectophore, which is specialized precociously to support the bud-colony, it would be possible theoretically to derive the Hippopodiid condition from that of the long-stemmed Physonect by imagining that with the disappearance of the pneumatophore, the pedicel or foot-stalk of the first nectophore grew continuously in length like that of the protosiphon (first gastrozooid), and that each successive nectophore was budded from the foot-stalk of the one before. Thus the nectosomal budding zone would remain near the siphosomal one, instead of being carried upwards further and further away from it as it is in Physonectae. In this way the lengthening of nectosome and siphosome
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