. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. 3o DISCOVERY REPORTS developed in the larva precociously (by heterochrony). It was then developed still further in the adult for the same purpose (swimming). Some adult Physonects took to swimming by jet propulsion, it might almost be said, because of an ' afterthought' on the part of an ancestral larva. The old suborder Disconanthae contains three forms Velella, Porpita and Porpema that are really the floating Tubulariid hydroid-phases of inconspicuous adult Codonid medusae known as Chryso- mit
. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. 3o DISCOVERY REPORTS developed in the larva precociously (by heterochrony). It was then developed still further in the adult for the same purpose (swimming). Some adult Physonects took to swimming by jet propulsion, it might almost be said, because of an ' afterthought' on the part of an ancestral larva. The old suborder Disconanthae contains three forms Velella, Porpita and Porpema that are really the floating Tubulariid hydroid-phases of inconspicuous adult Codonid medusae known as Chryso- mitra. There is nothing in their morphology in the least like the Siphonanthae, and it is possible that their pneumatophore has been acquired independently. They form a separate Order Chondrophora. Garstang (1946) interpreted the Conaria larva, but omitted reference to important papers by Delsman (1923) on the Conaria larva of Porpita and its development, and by Leloup (1929), who, after studying Velella at Villefranche, pointed out the homology between the Conaria larva and the actinula of Tubularia larynx, showing that the peculiar ' crimson cone' of Conaria corresponded with the ' gastric diaphragm' of Tubularia. This work of Leloup appears not to have been known to Garstang. Flrud Text-fig. 6. A, Actinula of Tubularia. After Leloup (1929). B, Conaria of Porpita. Based on Delsman (1923, figs. 16, 17, 18). XY= homologous planes. Text-fig. 6 will make this point clear. There is no need to endeavour, as Garstang did, to 'close the gap' between Disconanths and Siphonanths. The old order Siphonophora without doubt had a double origin, as Haeckel realized. As to the position of Pelagohydra, one is struck by the origin of the tentacles between the axial parenchyma in the meshes between the endoderm canals, from which the gonophores (gonozooids now reduced) spring. In Chondrophora Bigelow's sections show that the tentacles arise from the canals themselves. The difficulty of ex
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